Subject: daitch_mokotoff module

From: Dag Lem <[email-masked]>
Date: Fri, 03 Dec 2021 21:07:29 +0100

Hello,

Please find attached a patch for the daitch_mokotoff module.

This implements the Daitch-Mokotoff Soundex System, as described in
https://www.avotaynu.com/soundex.htm

The module is used in production at Finance Norway.

In order to verify correctness, I have compared generated soundex codes
with corresponding results from the implementation by Stephen P. Morse
at https://stevemorse.org/census/soundex.html

Where soundex codes differ, the daitch_mokotoff module has been found
to be correct. The Morse implementation uses a few unofficial rules,
and also has an error in the handling of adjacent identical code
digits. Please see daitch_mokotoff.c for further references and
comments.

For reference, detailed instructions for soundex code comparison are
attached.

Best regards

Dag Lem

diff --git a/contrib/Makefile b/contrib/Makefile
index 87bf87ab90..5e1111a729 100644
--- a/contrib/Makefile
+++ b/contrib/Makefile
@@ -14,6 +14,7 @@ SUBDIRS = \
 		btree_gist	\
 		citext		\
 		cube		\
+		daitch_mokotoff	\
 		dblink		\
 		dict_int	\
 		dict_xsyn	\
diff --git a/contrib/daitch_mokotoff/Makefile b/contrib/daitch_mokotoff/Makefile
new file mode 100644
index 0000000000..baec5e31d4
--- /dev/null
+++ b/contrib/daitch_mokotoff/Makefile
@@ -0,0 +1,25 @@
+# contrib/daitch_mokotoff/Makefile
+
+MODULE_big = daitch_mokotoff
+OBJS = \
+	$(WIN32RES) \
+	daitch_mokotoff.o
+
+EXTENSION = daitch_mokotoff
+DATA = daitch_mokotoff--1.0.sql
+PGFILEDESC = "daitch_mokotoff - Daitch-Mokotoff Soundex System"
+
+HEADERS = daitch_mokotoff.h
+
+REGRESS = daitch_mokotoff
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/daitch_mokotoff
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/contrib/daitch_mokotoff/daitch_mokotoff--1.0.sql b/contrib/daitch_mokotoff/daitch_mokotoff--1.0.sql
new file mode 100644
index 0000000000..0b5a643175
--- /dev/null
+++ b/contrib/daitch_mokotoff/daitch_mokotoff--1.0.sql
@@ -0,0 +1,8 @@
+/* contrib/daitch_mokotoff/daitch_mokotoff--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION daitch_mokotoff" to load this file. \quit
+
+CREATE FUNCTION daitch_mokotoff(text) RETURNS text
+AS 'MODULE_PATHNAME', 'daitch_mokotoff'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/contrib/daitch_mokotoff/daitch_mokotoff.c b/contrib/daitch_mokotoff/daitch_mokotoff.c
new file mode 100644
index 0000000000..9e66aee434
--- /dev/null
+++ b/contrib/daitch_mokotoff/daitch_mokotoff.c
@@ -0,0 +1,551 @@
+/*
+ * Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <[email-masked]>
+ *
+ * This implementation of the Daitch-Mokotoff Soundex System aims at high
+ * performance.
+ *
+ * - The processing of each phoneme is initiated by an O(1) table lookup.
+ * - For phonemes containing more than one character, a coding tree is traversed
+ *   to process the complete phoneme.
+ * - The (alternate) soundex codes are produced digit by digit in-place in
+ *   another tree structure.
+ *
+ *  References:
+ *
+ * https://www.avotaynu.com/soundex.htm
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * https://familypedia.fandom.com/wiki/Daitch-Mokotoff_Soundex
+ * https://stevemorse.org/phoneticinfo.htm (dmlat.php, dmsoundex.php)
+ * https://github.com/apache/commons-codec/ (dmrules.txt, DaitchMokotoffSoundex.java)
+ * https://metacpan.org/pod/Text::Phonetic (DaitchMokotoff.pm)
+ *
+ * A few notes on other implementations:
+ *
+ * - "J" is considered a vowel in dmlat.php
+ * - The official rules for "RS" are commented out in dmlat.php
+ * - Adjacent identical code digits are not collapsed correctly in dmsoundex.php
+ *   when double digit codes are involved. E.g. "BESST" yields 744300 instead of
+ *   743000 as for "BEST".
+ * - "Y" is not considered a vowel in DaitchMokotoffSoundex.java
+ * - Both dmlat.php and dmrules.txt have the same unofficial rules for "UE".
+ * - Coding of MN/NM + M/N differs between dmsoundex.php and DaitchMokotoffSoundex.java
+ * - Neither dmsoundex.php nor DaitchMokotoffSoundex.java yields all valid codes for e.g.
+ *   "CJC" (550000 540000 545000 450000 400000 440000).
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+*/
+
+#include "daitch_mokotoff.h"
+
+#ifndef DM_MAIN
+
+#include "postgres.h"
+#include "utils/builtins.h"
+#include "mb/pg_wchar.h"
+
+#else							/* DM_MAIN */
+
+#include <stdio.h>
+
+#endif							/* DM_MAIN */
+
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+/* Internal C implementation */
+static char *_daitch_mokotoff(char *word, char *soundex, size_t n);
+
+
+#ifndef DM_MAIN
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(daitch_mokotoff);
+Datum
+daitch_mokotoff(PG_FUNCTION_ARGS)
+{
+	text	   *arg = PG_GETARG_TEXT_PP(0);
+	char	   *string,
+			   *tmp_soundex;
+	text	   *soundex;
+
+	/*
+	 * The maximum theoretical soundex size is several KB, however in practice
+	 * anything but contrived synthetic inputs will yield a soundex size of
+	 * less than 100 bytes. We thus allocate and free a temporary work buffer,
+	 * and return only the actual soundex result.
+	 */
+	string = pg_server_to_any(text_to_cstring(arg), VARSIZE_ANY_EXHDR(arg), PG_UTF8);
+	tmp_soundex = palloc(DM_MAX_SOUNDEX_CHARS);
+
+	if (!(tmp_soundex && _daitch_mokotoff(string, tmp_soundex, DM_MAX_SOUNDEX_CHARS)))
+	{
+		pfree(tmp_soundex);
+		ereport(ERROR,
+				(errcode(ERRCODE_OUT_OF_MEMORY),
+				 errmsg("unable to allocate temporary memory for soundex")));
+	}
+
+	soundex = cstring_to_text(pg_any_to_server(tmp_soundex, strlen(tmp_soundex), PG_UTF8));
+	pfree(tmp_soundex);
+
+	PG_RETURN_TEXT_P(soundex);
+}
+
+#endif							/* DM_MAIN */
+
+
+typedef dm_node dm_nodes[DM_MAX_NODES];
+typedef dm_node * dm_leaves[DM_MAX_LEAVES];
+
+
+static const dm_node start_node = {
+	.soundex_length = 0,
+	.soundex = "000000 ",		/* Six digits + joining space */
+	.is_leaf = 0,
+	.last_update = 0,
+	.code_digit = '\0',
+	.prev_code_digits = {'\0', '\0'},
+	.next_code_digits = {'\0', '\0'},
+	.next_nodes = {NULL}
+};
+
+
+static void
+initialize_node(dm_node * node, int last_update)
+{
+	if (node->last_update < last_update)
+	{
+		node->prev_code_digits[0] = node->next_code_digits[0];
+		node->prev_code_digits[1] = node->next_code_digits[1];
+		node->next_code_digits[0] = '\0';
+		node->next_code_digits[1] = '\0';
+		node->is_leaf = 0;
+		node->last_update = last_update;
+	}
+}
+
+
+static void
+add_next_code_digit(dm_node * node, char code_digit)
+{
+	if (!node->next_code_digits[0])
+	{
+		node->next_code_digits[0] = code_digit;
+	}
+	else if (node->next_code_digits[0] != code_digit)
+	{
+		node->next_code_digits[1] = code_digit;
+	}
+}
+
+
+static void
+set_leaf(dm_leaves leaves_next, int *num_leaves_next, dm_node * node)
+{
+	if (!node->is_leaf)
+	{
+		node->is_leaf = 1;
+		leaves_next[(*num_leaves_next)++] = node;
+	}
+}
+
+
+static dm_node * find_or_create_node(dm_nodes nodes, int *num_nodes, dm_node * node, char code_digit)
+{
+	dm_node   **next_nodes;
+	dm_node    *next_node;
+
+	for (next_nodes = node->next_nodes; (next_node = *next_nodes); next_nodes++)
+	{
+		if (next_node->code_digit == code_digit)
+		{
+			return next_node;
+		}
+	}
+
+	next_node = &nodes[(*num_nodes)++];
+	*next_nodes = next_node;
+
+	*next_node = start_node;
+	memcpy(next_node->soundex, node->soundex, sizeof(next_node->soundex));
+	next_node->soundex_length = node->soundex_length;
+	next_node->soundex[next_node->soundex_length++] = code_digit;
+	next_node->code_digit = code_digit;
+
+	return next_node;
+}
+
+
+static int
+update_node(dm_nodes nodes, dm_node * node, int *num_nodes, dm_leaves leaves_next, int *num_leaves_next, int char_number, char next_code_digit, char next_code_digit_2)
+{
+	int			i;
+	int			num_dirty_nodes = 0;
+	dm_node    *dirty_nodes[2];
+
+	initialize_node(node, char_number);
+
+	if (node->soundex_length == DM_MAX_CODE_DIGITS)
+	{
+		/* Keep completed soundex code. */
+		set_leaf(leaves_next, num_leaves_next, node);
+		return 0;
+	}
+
+	if (next_code_digit == 'X' ||
+		node->prev_code_digits[0] == next_code_digit ||
+		node->prev_code_digits[1] == next_code_digit)
+	{
+		/* The code digit is the same as one of the previous (i.e. not added). */
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	if (next_code_digit != 'X' &&
+		(node->prev_code_digits[0] != next_code_digit ||
+		 node->prev_code_digits[1]))
+	{
+		/* The code digit is different from one of the previous (i.e. added). */
+		node = find_or_create_node(nodes, num_nodes, node, next_code_digit);
+		initialize_node(node, char_number);
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	for (i = 0; i < num_dirty_nodes; i++)
+	{
+		/* Add code digit leading to the current node. */
+		add_next_code_digit(dirty_nodes[i], next_code_digit);
+
+		if (next_code_digit_2)
+		{
+			update_node(nodes, dirty_nodes[i], num_nodes, leaves_next, num_leaves_next, char_number, next_code_digit_2, '\0');
+		}
+		else
+		{
+			set_leaf(leaves_next, num_leaves_next, dirty_nodes[i]);
+		}
+	}
+
+	return 1;
+}
+
+
+static int
+update_leaves(dm_nodes nodes, int *num_nodes, dm_leaves leaves[2], int *ix_leaves, int *num_leaves, int char_number, dm_codes codes)
+{
+	int			i,
+				j;
+	char	   *code;
+	int			num_leaves_next = 0;
+	int			ix_leaves_next = (*ix_leaves + 1) % 2;
+	int			finished = 1;
+
+	for (i = 0; i < *num_leaves; i++)
+	{
+		dm_node    *node = leaves[*ix_leaves][i];
+
+		/* One or two alternate code sequences. */
+		for (j = 0; j < 2 && (code = codes[j]) && code[0]; j++)
+		{
+			/* One or two sequential code digits. */
+			if (update_node(nodes, node, num_nodes, leaves[ix_leaves_next], &num_leaves_next, char_number, code[0], code[1]))
+			{
+				finished = 0;
+			}
+		}
+	}
+
+	*ix_leaves = ix_leaves_next;
+	*num_leaves = num_leaves_next;
+
+	return finished;
+}
+
+
+static const char tr_accents_iso8859_1[] =
+/*
+"ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
+*/
+"AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDsaaaaaaeceeeeiiiidnooooo/ouuuuydy";
+
+static char
+unaccent_iso8859_1(unsigned char c)
+{
+	return c >= 192 ? tr_accents_iso8859_1[c - 192] : c;
+}
+
+
+/* Convert an UTF-8 character to ISO-8859-1.
+ * Unconvertable characters are returned as '?'.
+ * NB! Beware of the domain specific conversion of Ą, Ę, and Ţ/Ț.
+ */
+static char
+utf8_to_iso8859_1(char *str, int *len)
+{
+	const char	unknown = '?';
+	unsigned char c;
+	unsigned int code_point;
+
+	*len = 1;
+	c = (unsigned char) str[0];
+	if (c < 0x80)
+	{
+		/* ASCII code point. */
+		return c;
+	}
+	else if (c < 0xE0)
+	{
+		/* Two-byte character. */
+		if (!str[1])
+		{
+			/* The UTF-8 character is cut short (invalid code point). */
+			return unknown;
+		}
+		*len = 2;
+		code_point = ((c & 0x1F) << 6) | (str[1] & 0x3F);
+		if (code_point < 0x100)
+		{
+			/* ISO-8859-1 code point. */
+			return code_point;
+		}
+		else if (code_point == 0x0104 || code_point == 0x0105)
+		{
+			/* Ą/ą */
+			return '[';
+		}
+		else if (code_point == 0x0118 || code_point == 0x0119)
+		{
+			/* Ę/ę */
+			return '\\';
+		}
+		else if (code_point == 0x0162 || code_point == 0x0163 ||
+				 code_point == 0x021A || code_point == 0x021B)
+		{
+			/* Ţ/ţ or Ț/ț */
+			return ']';
+		}
+		else
+		{
+			return unknown;
+		}
+	}
+	else if (c < 0xF0)
+	{
+		/* Three-byte character. */
+		if (!str[2])
+		{
+			/* The UTF-8 character is cut short (invalid code point). */
+			*len = 2;
+		}
+		else
+		{
+			*len = 3;
+		}
+		return unknown;
+	}
+	else
+	{
+		/* Four-byte character. */
+		if (!str[3])
+		{
+			/* The UTF-8 character is cut short (invalid code point). */
+			*len = 3;
+		}
+		else
+		{
+			*len = 4;
+		}
+		return unknown;
+	}
+}
+
+
+static char
+read_char(char *str, int *len)
+{
+	return toupper(unaccent_iso8859_1(utf8_to_iso8859_1(str, len)));
+}
+
+
+static char
+read_valid_char(char *str, int *len)
+{
+	int			c;
+	int			i,
+				ilen;
+
+	for (i = 0, ilen = 0; (c = read_char(&str[i], &ilen)) && (c < 'A' || c > ']'); i += ilen)
+	{
+	}
+
+	*len = i + ilen;
+	return c;
+}
+
+
+static char *
+_daitch_mokotoff(char *word, char *soundex, size_t n)
+{
+	int			c,
+				cmp;
+	int			i,
+				ilen,
+				i_ok,
+				j,
+				jlen,
+				k;
+	int			first_letter = 1;
+	int			ix_leaves = 0;
+	int			num_nodes = 0,
+				num_leaves = 0;
+	dm_letter  *letter,
+			   *letters;
+	dm_codes   *codes_ok,
+				codes;
+
+	dm_node    *nodes = malloc(sizeof(dm_nodes));
+	dm_leaves  *leaves = malloc(2 * sizeof(dm_leaves));
+
+	if (!nodes || !leaves)
+	{
+		/* Out of memory - clean up and return. */
+		free(leaves);
+		free(nodes);
+		*soundex = '\0';
+		return NULL;
+	}
+
+	/* Starting point. */
+	nodes[num_nodes++] = start_node;
+	leaves[ix_leaves][num_leaves++] = &nodes[0];
+
+	for (i = 0; (c = read_valid_char(&word[i], &ilen)); i += ilen)
+	{
+		/* First letter in sequence. */
+		letter = &letter_[c - 'A'];
+		codes_ok = letter->codes;
+		i_ok = i;
+
+		/* Subsequent letters. */
+		for (j = i + ilen; (letters = letter->letters) && (c = read_valid_char(&word[j], &jlen)); j += jlen)
+		{
+			for (k = 0; (cmp = letters[k].letter); k++)
+			{
+				if (cmp == c)
+				{
+					/* Coding for letter found. */
+					break;
+				}
+			}
+			if (!cmp)
+			{
+				/* The sequence of letters has no coding. */
+				break;
+			}
+
+			letter = &letters[k];
+			if (letter->codes)
+			{
+				codes_ok = letter->codes;
+				i_ok = j;
+				ilen = jlen;
+			}
+		}
+
+		/* Determine which code to use. */
+		if (first_letter)
+		{
+			/* This is the first letter. */
+			j = 0;
+			first_letter = 0;
+		}
+		else if ((c = read_valid_char(&word[i_ok + ilen], &jlen)) && strchr(DM_VOWELS, c))
+		{
+			/* The next letter is a vowel. */
+			j = 1;
+		}
+		else
+		{
+			/* All other cases. */
+			j = 2;
+		}
+		memcpy(codes, codes_ok[j], sizeof(codes));
+
+		/* Update leaves. */
+		if (update_leaves(nodes, &num_nodes, leaves, &ix_leaves, &num_leaves, i, codes))
+		{
+			/* All soundex codes are completed to six digits. */
+			break;
+		}
+
+		/* Prepare for next letter sequence. */
+		i = i_ok;
+	}
+
+	/* Concatenate all generated soundex codes. */
+	for (i = 0, j = 0; i < num_leaves && j + DM_MAX_CODE_DIGITS + 1 <= n; i++, j += DM_MAX_CODE_DIGITS + 1)
+	{
+		memcpy(&soundex[j], leaves[ix_leaves][i]->soundex, DM_MAX_CODE_DIGITS + 1);
+	}
+
+	/* Terminate string. */
+	soundex[j - (j != 0)] = '\0';
+
+	free(leaves);
+	free(nodes);
+
+	return soundex;
+}
+
+
+#ifdef DM_MAIN
+
+/* For testing */
+
+int
+main(int argc, char **argv)
+{
+	char	   *soundex;
+
+	if (argc != 2)
+	{
+		fprintf(stderr, "Usage: %s string\n", argv[0]);
+		return -1;
+	}
+
+	soundex = malloc(DM_MAX_SOUNDEX_CHARS);
+
+	if (!_daitch_mokotoff(argv[1], soundex, DM_MAX_SOUNDEX_CHARS))
+	{
+		free(soundex);
+		fprintf(stderr, "Unable to allocate memory for soundex trees\n");
+		return -1;
+	}
+
+	printf("%s\n", soundex);
+	free(soundex);
+
+	return 0;
+}
+
+#endif
diff --git a/contrib/daitch_mokotoff/daitch_mokotoff.control b/contrib/daitch_mokotoff/daitch_mokotoff.control
new file mode 100644
index 0000000000..c5aed8e46e
--- /dev/null
+++ b/contrib/daitch_mokotoff/daitch_mokotoff.control
@@ -0,0 +1,5 @@
+# daitch_mokotoff extension
+comment = 'Daitch-Mokotoff Soundex System'
+default_version = '1.0'
+module_pathname = '$libdir/daitch_mokotoff'
+relocatable = true
diff --git a/contrib/daitch_mokotoff/daitch_mokotoff.h b/contrib/daitch_mokotoff/daitch_mokotoff.h
new file mode 100644
index 0000000000..8fcb98f1cf
--- /dev/null
+++ b/contrib/daitch_mokotoff/daitch_mokotoff.h
@@ -0,0 +1,1110 @@
+/*
+ * Types and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <[email-masked]>
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include <stdlib.h>
+
+#define DM_MAX_CODE_DIGITS 6
+#define DM_MAX_ALTERNATE_CODES 5
+#define DM_MAX_NODES 1564
+#define DM_MAX_LEAVES 1250
+#define DM_MAX_SOUNDEX_CHARS (DM_MAX_NODES*(DM_MAX_CODE_DIGITS + 1))
+#define DM_VOWELS "AEIOUY"
+
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[2];	/* One or two alternate code sequences */
+
+struct dm_letter
+{
+	char		letter;
+	struct dm_letter *letters;
+	dm_codes   *codes;
+};
+
+struct dm_node
+{
+	int			soundex_length;
+	char		soundex[DM_MAX_CODE_DIGITS + 1];
+	int			is_leaf;
+	int			last_update;
+	char		code_digit;
+
+	/*
+	 * One or two alternate code digits leading to this node - repeated code
+	 * digits and 'X' lead back to the same node.
+	 */
+	char		prev_code_digits[2];
+	char		next_code_digits[2];
+	struct dm_node *next_nodes[DM_MAX_ALTERNATE_CODES + 1];
+};
+
+typedef struct dm_letter dm_letter;
+typedef struct dm_node dm_node;
+
+static dm_codes codes_0_1_X[] =
+{
+	{
+		"0"
+	},
+	{
+		"1"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_0_7_X[] =
+{
+	{
+		"0"
+	},
+	{
+		"7"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_0_X_X[] =
+{
+	{
+		"0"
+	},
+	{
+		"X"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_1_1_X[] =
+{
+	{
+		"1"
+	},
+	{
+		"1"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_1_X_X[] =
+{
+	{
+		"1"
+	},
+	{
+		"X"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_1or4_Xor4_Xor4[] =
+{
+	{
+		"1", "4"
+	},
+	{
+		"X", "4"
+	},
+	{
+		"X", "4"
+	}
+};
+static dm_codes codes_2_43_43[] =
+{
+	{
+		"2"
+	},
+	{
+		"43"
+	},
+	{
+		"43"
+	}
+};
+static dm_codes codes_2_4_4[] =
+{
+	{
+		"2"
+	},
+	{
+		"4"
+	},
+	{
+		"4"
+	}
+};
+static dm_codes codes_3_3_3[] =
+{
+	{
+		"3"
+	},
+	{
+		"3"
+	},
+	{
+		"3"
+	}
+};
+static dm_codes codes_3or4_3or4_3or4[] =
+{
+	{
+		"3", "4"
+	},
+	{
+		"3", "4"
+	},
+	{
+		"3", "4"
+	}
+};
+static dm_codes codes_4_4_4[] =
+{
+	{
+		"4"
+	},
+	{
+		"4"
+	},
+	{
+		"4"
+	}
+};
+static dm_codes codes_5_54_54[] =
+{
+	{
+		"5"
+	},
+	{
+		"54"
+	},
+	{
+		"54"
+	}
+};
+static dm_codes codes_5_5_5[] =
+{
+	{
+		"5"
+	},
+	{
+		"5"
+	},
+	{
+		"5"
+	}
+};
+static dm_codes codes_5_5_X[] =
+{
+	{
+		"5"
+	},
+	{
+		"5"
+	},
+	{
+		"X"
+	}
+};
+static dm_codes codes_5or45_5or45_5or45[] =
+{
+	{
+		"5", "45"
+	},
+	{
+		"5", "45"
+	},
+	{
+		"5", "45"
+	}
+};
+static dm_codes codes_5or4_5or4_5or4[] =
+{
+	{
+		"5", "4"
+	},
+	{
+		"5", "4"
+	},
+	{
+		"5", "4"
+	}
+};
+static dm_codes codes_66_66_66[] =
+{
+	{
+		"66"
+	},
+	{
+		"66"
+	},
+	{
+		"66"
+	}
+};
+static dm_codes codes_6_6_6[] =
+{
+	{
+		"6"
+	},
+	{
+		"6"
+	},
+	{
+		"6"
+	}
+};
+static dm_codes codes_7_7_7[] =
+{
+	{
+		"7"
+	},
+	{
+		"7"
+	},
+	{
+		"7"
+	}
+};
+static dm_codes codes_8_8_8[] =
+{
+	{
+		"8"
+	},
+	{
+		"8"
+	},
+	{
+		"8"
+	}
+};
+static dm_codes codes_94or4_94or4_94or4[] =
+{
+	{
+		"94", "4"
+	},
+	{
+		"94", "4"
+	},
+	{
+		"94", "4"
+	}
+};
+static dm_codes codes_9_9_9[] =
+{
+	{
+		"9"
+	},
+	{
+		"9"
+	},
+	{
+		"9"
+	}
+};
+static dm_codes codes_X_X_6orX[] =
+{
+	{
+		"X"
+	},
+	{
+		"X"
+	},
+	{
+		"6", "X"
+	}
+};
+
+static dm_letter letter_A[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'U', NULL, codes_0_7_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CH[] =
+{
+	{
+		'S', NULL, codes_5_54_54
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CS[] =
+{
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CZ[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_C[] =
+{
+	{
+		'H', letter_CH, codes_5or4_5or4_5or4
+	},
+	{
+		'K', NULL, codes_5or45_5or45_5or45
+	},
+	{
+		'S', letter_CS, codes_4_4_4
+	},
+	{
+		'Z', letter_CZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DR[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DS[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DZ[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_D[] =
+{
+	{
+		'R', letter_DR, NULL
+	},
+	{
+		'S', letter_DS, codes_4_4_4
+	},
+	{
+		'T', NULL, codes_3_3_3
+	},
+	{
+		'Z', letter_DZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_E[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'U', NULL, codes_1_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_F[] =
+{
+	{
+		'B', NULL, codes_7_7_7
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_I[] =
+{
+	{
+		'A', NULL, codes_1_X_X
+	},
+	{
+		'E', NULL, codes_1_X_X
+	},
+	{
+		'O', NULL, codes_1_X_X
+	},
+	{
+		'U', NULL, codes_1_X_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_K[] =
+{
+	{
+		'H', NULL, codes_5_5_5
+	},
+	{
+		'S', NULL, codes_5_54_54
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_M[] =
+{
+	{
+		'N', NULL, codes_66_66_66
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_N[] =
+{
+	{
+		'M', NULL, codes_66_66_66
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_O[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_P[] =
+{
+	{
+		'F', NULL, codes_7_7_7
+	},
+	{
+		'H', NULL, codes_7_7_7
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_R[] =
+{
+	{
+		'S', NULL, codes_94or4_94or4_94or4
+	},
+	{
+		'Z', NULL, codes_94or4_94or4_94or4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTSC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTS[] =
+{
+	{
+		'C', letter_SCHTSC, NULL
+	},
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHT[] =
+{
+	{
+		'C', letter_SCHTC, NULL
+	},
+	{
+		'S', letter_SCHTS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCH[] =
+{
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', letter_SCHT, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SC[] =
+{
+	{
+		'H', letter_SCH, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHTC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHTS[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHT[] =
+{
+	{
+		'C', letter_SHTC, NULL
+	},
+	{
+		'S', letter_SHTS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SH[] =
+{
+	{
+		'C', letter_SHC, NULL
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', letter_SHT, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STR[] =
+{
+	{
+		'S', NULL, codes_2_4_4
+	},
+	{
+		'Z', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STSC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STS[] =
+{
+	{
+		'C', letter_STSC, NULL
+	},
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ST[] =
+{
+	{
+		'C', letter_STC, NULL
+	},
+	{
+		'R', letter_STR, NULL
+	},
+	{
+		'S', letter_STS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SZC[] =
+{
+	{
+		'S', NULL, codes_2_4_4
+	},
+	{
+		'Z', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SZ[] =
+{
+	{
+		'C', letter_SZC, NULL
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', NULL, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_S[] =
+{
+	{
+		'C', letter_SC, codes_2_4_4
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'H', letter_SH, codes_4_4_4
+	},
+	{
+		'T', letter_ST, codes_2_43_43
+	},
+	{
+		'Z', letter_SZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TR[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TS[] =
+{
+	{
+		'C', letter_TSC, NULL
+	},
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTS[] =
+{
+	{
+		'C', letter_TTSC, NULL
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TT[] =
+{
+	{
+		'C', letter_TTC, NULL
+	},
+	{
+		'S', letter_TTS, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TZ[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_T[] =
+{
+	{
+		'C', letter_TC, codes_4_4_4
+	},
+	{
+		'H', NULL, codes_3_3_3
+	},
+	{
+		'R', letter_TR, NULL
+	},
+	{
+		'S', letter_TS, codes_4_4_4
+	},
+	{
+		'T', letter_TT, NULL
+	},
+	{
+		'Z', letter_TZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_U[] =
+{
+	{
+		'E', NULL, codes_0_X_X
+	},
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZDZ[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZD[] =
+{
+	{
+		'Z', letter_ZDZ, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZHDZ[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZHD[] =
+{
+	{
+		'Z', letter_ZHDZ, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZH[] =
+{
+	{
+		'D', letter_ZHD, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZS[] =
+{
+	{
+		'C', letter_ZSC, NULL
+	},
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_Z[] =
+{
+	{
+		'D', letter_ZD, codes_2_43_43
+	},
+	{
+		'H', letter_ZH, codes_4_4_4
+	},
+	{
+		'S', letter_ZS, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_[] =
+{
+	{
+		'A', letter_A, codes_0_X_X
+	},
+	{
+		'B', NULL, codes_7_7_7
+	},
+	{
+		'C', letter_C, codes_5or4_5or4_5or4
+	},
+	{
+		'D', letter_D, codes_3_3_3
+	},
+	{
+		'E', letter_E, codes_0_X_X
+	},
+	{
+		'F', letter_F, codes_7_7_7
+	},
+	{
+		'G', NULL, codes_5_5_5
+	},
+	{
+		'H', NULL, codes_5_5_X
+	},
+	{
+		'I', letter_I, codes_0_X_X
+	},
+	{
+		'J', NULL, codes_1or4_Xor4_Xor4
+	},
+	{
+		'K', letter_K, codes_5_5_5
+	},
+	{
+		'L', NULL, codes_8_8_8
+	},
+	{
+		'M', letter_M, codes_6_6_6
+	},
+	{
+		'N', letter_N, codes_6_6_6
+	},
+	{
+		'O', letter_O, codes_0_X_X
+	},
+	{
+		'P', letter_P, codes_7_7_7
+	},
+	{
+		'Q', NULL, codes_5_5_5
+	},
+	{
+		'R', letter_R, codes_9_9_9
+	},
+	{
+		'S', letter_S, codes_4_4_4
+	},
+	{
+		'T', letter_T, codes_3_3_3
+	},
+	{
+		'U', letter_U, codes_0_X_X
+	},
+	{
+		'V', NULL, codes_7_7_7
+	},
+	{
+		'W', NULL, codes_7_7_7
+	},
+	{
+		'X', NULL, codes_5_54_54
+	},
+	{
+		'Y', NULL, codes_1_X_X
+	},
+	{
+		'Z', letter_Z, codes_4_4_4
+	},
+	{
+		'a', NULL, codes_X_X_6orX
+	},
+	{
+		'e', NULL, codes_X_X_6orX
+	},
+	{
+		't', NULL, codes_3or4_3or4_3or4
+	},
+	{
+		'\0'
+	}
+};
diff --git a/contrib/daitch_mokotoff/daitch_mokotoff_header.pl b/contrib/daitch_mokotoff/daitch_mokotoff_header.pl
new file mode 100755
index 0000000000..26e67fe5df
--- /dev/null
+++ b/contrib/daitch_mokotoff/daitch_mokotoff_header.pl
@@ -0,0 +1,274 @@
+#!/bin/perl
+#
+# Generation of types and lookup tables for Daitch-Mokotoff soundex.
+#
+# Copyright (c) 2021 Finance Norway
+# Author: Dag Lem <[email-masked]>
+#
+# Permission to use, copy, modify, and distribute this software and its
+# documentation for any purpose, without fee, and without a written agreement
+# is hereby granted, provided that the above copyright notice and this
+# paragraph and the following two paragraphs appear in all copies.
+#
+# IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+# DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+# LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+# DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+# AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+# ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+# PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+#
+
+use strict;
+use warnings;
+use utf8;
+use open IO => ':utf8', ':std';
+use Data::Dumper;
+
+# Parse code table and generate tree for letter transitions.
+my %codes;
+my %alternates;
+my $table = [{}, [["","",""]]];
+while (<DATA>) {
+	chomp;
+	my ($letters, $codes) = split(/\s+/);
+	my @codes = map { [ split(/\|/) ] } split(/,/, $codes);
+
+	# Find alternate code transitions for calculation of storage.
+	# The first character can never yield more than two alternate codes, and is not considered here.
+	for my $c (@codes[1..2]) {
+		if (@$c > 1) {
+			for my $i (0..1) {
+				my ($a, $b) = (substr($c->[$i], -1, 1), substr($c->[($i + 1)%2], 0, 1));
+				$alternates{$a}{$b} = 1 if $a ne $b;
+			}
+		}
+	}
+	my $key = "codes_" . join("_", map { join("or", @$_) } @codes);
+	my $val = join(",\n", map { "\t{\n\t\t" . join(", ", map { "\"$_\"" } @$_) . "\n\t}" } @codes);
+	$codes{$key} = $val;
+
+	for my $letter (split(/,/, $letters)) {
+		my $ref = $table->[0];
+		# Link each character to the next in the letter combination.
+		my @c = split(//, $letter);
+		my $last_c = pop(@c);
+		for my $c (@c) {
+			$ref->{$c} //= [ {}, undef ];
+			$ref->{$c}[0] //= {};
+			$ref = $ref->{$c}[0];
+		}
+		# The sound code for the letter combination is stored at the last character.
+		$ref->{$last_c}[1] = $key;
+	}
+}
+close(DATA);
+
+# Find the maximum number of alternate codes in one position.
+my $alt_x = $alternates{"X"};
+while (my ($k, $v) = each %alternates) {
+	if (defined delete $v->{"X"}) {
+		for my $x (keys %$alt_x) {
+			$v->{$x} = 1;
+		}
+	}
+}
+my $max_alt = (reverse sort (2, map { scalar keys %$_ } values %alternates))[0];
+
+# The maximum number of nodes and leaves in the soundex tree.
+# These are safe estimates, but in practice somewhat higher than the actual maximums.
+# Note that the first character can never yield more than two alternate codes,
+# hence the calculations are performed as sums of two subtrees.
+my $digits = 6;
+# Number of nodes (sum of geometric progression).
+my $max_nodes = 2 + 2*(1 - $max_alt**($digits - 1))/(1 - $max_alt);
+# Number of leaves (exponential of base number).
+my $max_leaves = 2*$max_alt**($digits - 2);
+
+print <<EOF;
+/*
+ * Types and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <dag\@nimrod.no>
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include <stdlib.h>
+
+#define DM_MAX_CODE_DIGITS $digits
+#define DM_MAX_ALTERNATE_CODES $max_alt
+#define DM_MAX_NODES $max_nodes
+#define DM_MAX_LEAVES $max_leaves
+#define DM_MAX_SOUNDEX_CHARS (DM_MAX_NODES*(DM_MAX_CODE_DIGITS + 1))
+#define DM_VOWELS "AEIOUY"
+
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[2];	/* One or two alternate code sequences */
+
+struct dm_letter
+{
+	char		letter;
+	struct dm_letter *letters;
+	dm_codes   *codes;
+};
+
+struct dm_node
+{
+	int			soundex_length;
+	char		soundex[DM_MAX_CODE_DIGITS + 1];
+	int			is_leaf;
+	int			last_update;
+	char		code_digit;
+
+	/*
+	 * One or two alternate code digits leading to this node - repeated code
+	 * digits and 'X' lead back to the same node.
+	 */
+	char		prev_code_digits[2];
+	char		next_code_digits[2];
+	struct dm_node *next_nodes[DM_MAX_ALTERNATE_CODES + 1];
+};
+
+typedef struct dm_letter dm_letter;
+typedef struct dm_node dm_node;
+
+EOF
+
+for my $key (sort keys %codes) {
+	print "static dm_codes $key\[\] =\n{\n" . $codes{$key} . "\n};\n";
+}
+
+print "\n";
+
+sub hash2code {
+	my ($ref, $letter) = @_;
+
+	my @letters = ();
+
+	my $h = $ref->[0];
+	for my $key (sort keys %$h) {
+		$ref = $h->{$key};
+		my $children = "NULL";
+		if (defined $ref->[0]) {
+			$children = "letter_$letter$key";
+			hash2code($ref, "$letter$key");
+		}
+		my $codes = $ref->[1] // "NULL";
+		push(@letters, "\t{\n\t\t'$key', $children, $codes\n\t}");
+	}
+
+	print "static dm_letter letter_$letter\[\] =\n{\n";
+	for (@letters) {
+		print "$_,\n";
+	}
+	print "\t{\n\t\t'\\0'\n\t}\n";
+	print "};\n";
+}
+
+hash2code($table, '');
+
+
+# Table adapted from https://www.jewishgen.org/InfoFiles/Soundex.html
+#
+# X = NC (not coded)
+#
+# Note that the following letters are coded with substitute letters
+#
+# Ą => a (use '[' for table lookup)
+# Ę => e (use '\\' for table lookup)
+# Ţ => t (use ']' for table lookup)
+#
+
+__DATA__
+AI,AJ,AY				0,1,X
+AU						0,7,X
+a						X,X,6|X
+A						0,X,X
+B						7,7,7
+CHS						5,54,54
+CH						5|4,5|4,5|4
+CK						5|45,5|45,5|45
+CZ,CS,CSZ,CZS			4,4,4
+C						5|4,5|4,5|4
+DRZ,DRS					4,4,4
+DS,DSH,DSZ				4,4,4
+DZ,DZH,DZS				4,4,4
+D,DT					3,3,3
+EI,EJ,EY				0,1,X
+EU						1,1,X
+e						X,X,6|X
+E						0,X,X
+FB						7,7,7
+F						7,7,7
+G						5,5,5
+H						5,5,X
+IA,IE,IO,IU				1,X,X
+I						0,X,X
+J						1|4,X|4,X|4
+KS						5,54,54
+KH						5,5,5
+K						5,5,5
+L						8,8,8
+MN						66,66,66
+M						6,6,6
+NM						66,66,66
+N						6,6,6
+OI,OJ,OY				0,1,X
+O						0,X,X
+P,PF,PH					7,7,7
+Q						5,5,5
+RZ,RS					94|4,94|4,94|4
+R						9,9,9
+SCHTSCH,SCHTSH,SCHTCH	2,4,4
+SCH						4,4,4
+SHTCH,SHCH,SHTSH		2,4,4
+SHT,SCHT,SCHD			2,43,43
+SH						4,4,4
+STCH,STSCH,SC			2,4,4
+STRZ,STRS,STSH			2,4,4
+ST						2,43,43
+SZCZ,SZCS				2,4,4
+SZT,SHD,SZD,SD			2,43,43
+SZ						4,4,4
+S						4,4,4
+TCH,TTCH,TTSCH			4,4,4
+TH						3,3,3
+TRZ,TRS					4,4,4
+TSCH,TSH				4,4,4
+TS,TTS,TTSZ,TC			4,4,4
+TZ,TTZ,TZS,TSZ			4,4,4
+t						3|4,3|4,3|4
+T						3,3,3
+UI,UJ,UY				0,1,X
+U,UE					0,X,X
+V						7,7,7
+W						7,7,7
+X						5,54,54
+Y						1,X,X
+ZDZ,ZDZH,ZHDZH			2,4,4
+ZD,ZHD					2,43,43
+ZH,ZS,ZSCH,ZSH			4,4,4
+Z						4,4,4
diff --git a/contrib/daitch_mokotoff/expected/daitch_mokotoff.out b/contrib/daitch_mokotoff/expected/daitch_mokotoff.out
new file mode 100644
index 0000000000..b7db809746
--- /dev/null
+++ b/contrib/daitch_mokotoff/expected/daitch_mokotoff.out
@@ -0,0 +1,451 @@
+CREATE EXTENSION daitch_mokotoff;
+SELECT daitch_mokotoff('GOLDEN');
+ daitch_mokotoff 
+-----------------
+ 583600
+(1 row)
+
+SELECT daitch_mokotoff('Alpert');
+ daitch_mokotoff 
+-----------------
+ 087930
+(1 row)
+
+SELECT daitch_mokotoff('Breuer');
+ daitch_mokotoff 
+-----------------
+ 791900
+(1 row)
+
+SELECT daitch_mokotoff('Freud');
+ daitch_mokotoff 
+-----------------
+ 793000
+(1 row)
+
+SELECT daitch_mokotoff('Haber');
+ daitch_mokotoff 
+-----------------
+ 579000
+(1 row)
+
+SELECT daitch_mokotoff('Manheim');
+ daitch_mokotoff 
+-----------------
+ 665600
+(1 row)
+
+SELECT daitch_mokotoff('Mintz');
+ daitch_mokotoff 
+-----------------
+ 664000
+(1 row)
+
+SELECT daitch_mokotoff('Topf');
+ daitch_mokotoff 
+-----------------
+ 370000
+(1 row)
+
+SELECT daitch_mokotoff('Kleinman');
+ daitch_mokotoff 
+-----------------
+ 586660
+(1 row)
+
+SELECT daitch_mokotoff('Ben Aron');
+ daitch_mokotoff 
+-----------------
+ 769600
+(1 row)
+
+SELECT daitch_mokotoff('AUERBACH');
+ daitch_mokotoff 
+-----------------
+ 097500 097400
+(1 row)
+
+SELECT daitch_mokotoff('OHRBACH');
+ daitch_mokotoff 
+-----------------
+ 097500 097400
+(1 row)
+
+SELECT daitch_mokotoff('LIPSHITZ');
+ daitch_mokotoff 
+-----------------
+ 874400
+(1 row)
+
+SELECT daitch_mokotoff('LIPPSZYC');
+ daitch_mokotoff 
+-----------------
+ 874500 874400
+(1 row)
+
+SELECT daitch_mokotoff('LEWINSKY');
+ daitch_mokotoff 
+-----------------
+ 876450
+(1 row)
+
+SELECT daitch_mokotoff('LEVINSKI');
+ daitch_mokotoff 
+-----------------
+ 876450
+(1 row)
+
+SELECT daitch_mokotoff('SZLAMAWICZ');
+ daitch_mokotoff 
+-----------------
+ 486740
+(1 row)
+
+SELECT daitch_mokotoff('SHLAMOVITZ');
+ daitch_mokotoff 
+-----------------
+ 486740
+(1 row)
+
+SELECT daitch_mokotoff('Ceniow');
+ daitch_mokotoff 
+-----------------
+ 567000 467000
+(1 row)
+
+SELECT daitch_mokotoff('Tsenyuv');
+ daitch_mokotoff 
+-----------------
+ 467000
+(1 row)
+
+SELECT daitch_mokotoff('Holubica');
+ daitch_mokotoff 
+-----------------
+ 587500 587400
+(1 row)
+
+SELECT daitch_mokotoff('Golubitsa');
+ daitch_mokotoff 
+-----------------
+ 587400
+(1 row)
+
+SELECT daitch_mokotoff('Przemysl');
+ daitch_mokotoff 
+-----------------
+ 794648 746480
+(1 row)
+
+SELECT daitch_mokotoff('Pshemeshil');
+ daitch_mokotoff 
+-----------------
+ 746480
+(1 row)
+
+SELECT daitch_mokotoff('Rosochowaciec');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 945755 945754 945745 945744 944755 944754 944745 944744
+(1 row)
+
+SELECT daitch_mokotoff('Rosokhovatsets');
+ daitch_mokotoff 
+-----------------
+ 945744
+(1 row)
+
+SELECT daitch_mokotoff('Peters');
+ daitch_mokotoff 
+-----------------
+ 739400 734000
+(1 row)
+
+SELECT daitch_mokotoff('Peterson');
+ daitch_mokotoff 
+-----------------
+ 739460 734600
+(1 row)
+
+SELECT daitch_mokotoff('Moskowitz');
+ daitch_mokotoff 
+-----------------
+ 645740
+(1 row)
+
+SELECT daitch_mokotoff('Moskovitz');
+ daitch_mokotoff 
+-----------------
+ 645740
+(1 row)
+
+SELECT daitch_mokotoff('Auerbach');
+ daitch_mokotoff 
+-----------------
+ 097500 097400
+(1 row)
+
+SELECT daitch_mokotoff('Uhrbach');
+ daitch_mokotoff 
+-----------------
+ 097500 097400
+(1 row)
+
+SELECT daitch_mokotoff('Jackson');
+       daitch_mokotoff       
+-----------------------------
+ 154600 145460 454600 445460
+(1 row)
+
+SELECT daitch_mokotoff('Jackson-Jackson');
+                            daitch_mokotoff                            
+-----------------------------------------------------------------------
+ 154654 154645 154644 145465 145464 454654 454645 454644 445465 445464
+(1 row)
+
+SELECT daitch_mokotoff('Müller');
+ daitch_mokotoff 
+-----------------
+ 689000
+(1 row)
+
+SELECT daitch_mokotoff('schmidt');
+ daitch_mokotoff 
+-----------------
+ 463000
+(1 row)
+
+SELECT daitch_mokotoff('schneider');
+ daitch_mokotoff 
+-----------------
+ 463900
+(1 row)
+
+SELECT daitch_mokotoff('fischer');
+ daitch_mokotoff 
+-----------------
+ 749000
+(1 row)
+
+SELECT daitch_mokotoff('weber');
+ daitch_mokotoff 
+-----------------
+ 779000
+(1 row)
+
+SELECT daitch_mokotoff('meyer');
+ daitch_mokotoff 
+-----------------
+ 619000
+(1 row)
+
+SELECT daitch_mokotoff('wagner');
+ daitch_mokotoff 
+-----------------
+ 756900
+(1 row)
+
+SELECT daitch_mokotoff('schulz');
+ daitch_mokotoff 
+-----------------
+ 484000
+(1 row)
+
+SELECT daitch_mokotoff('becker');
+ daitch_mokotoff 
+-----------------
+ 759000 745900
+(1 row)
+
+SELECT daitch_mokotoff('hoffmann');
+ daitch_mokotoff 
+-----------------
+ 576600
+(1 row)
+
+SELECT daitch_mokotoff('schäfer');
+ daitch_mokotoff 
+-----------------
+ 479000
+(1 row)
+
+SELECT daitch_mokotoff('Straßburg');
+ daitch_mokotoff 
+-----------------
+ 294795
+(1 row)
+
+SELECT daitch_mokotoff('Strasburg');
+ daitch_mokotoff 
+-----------------
+ 294795
+(1 row)
+
+SELECT daitch_mokotoff('Éregon');
+ daitch_mokotoff 
+-----------------
+ 095600
+(1 row)
+
+SELECT daitch_mokotoff('Eregon');
+ daitch_mokotoff 
+-----------------
+ 095600
+(1 row)
+
+SELECT daitch_mokotoff('AKSSOL');
+ daitch_mokotoff 
+-----------------
+ 054800
+(1 row)
+
+SELECT daitch_mokotoff('GERSCHFELD');
+       daitch_mokotoff       
+-----------------------------
+ 594578 594783 545783 547830
+(1 row)
+
+SELECT daitch_mokotoff('OBrien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('''OBrien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('O''Brien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('OB''rien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('OBr''ien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('OBri''en');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('OBrie''n');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('OBrien''');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('KINGSMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('-KINGSMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('K-INGSMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KI-NGSMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KIN-GSMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KING-SMITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KINGS-MITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KINGSM-ITH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KINGSMI-TH');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KINGSMIT-H');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff('KINGSMITH-');
+ daitch_mokotoff 
+-----------------
+ 565463
+(1 row)
+
+SELECT daitch_mokotoff(E' \t\n\r Washington \t\n\r ');
+ daitch_mokotoff 
+-----------------
+ 746536
+(1 row)
+
+SELECT daitch_mokotoff('Washington');
+ daitch_mokotoff 
+-----------------
+ 746536
+(1 row)
+
+SELECT daitch_mokotoff('ţamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
+SELECT daitch_mokotoff('țamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
+SELECT daitch_mokotoff('CJC');
+              daitch_mokotoff              
+-------------------------------------------
+ 550000 540000 545000 450000 400000 440000
+(1 row)
+
diff --git a/contrib/daitch_mokotoff/sql/daitch_mokotoff.sql b/contrib/daitch_mokotoff/sql/daitch_mokotoff.sql
new file mode 100644
index 0000000000..eafc24ee87
--- /dev/null
+++ b/contrib/daitch_mokotoff/sql/daitch_mokotoff.sql
@@ -0,0 +1,121 @@
+CREATE EXTENSION daitch_mokotoff;
+
+
+-- https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('GOLDEN');
+SELECT daitch_mokotoff('Alpert');
+SELECT daitch_mokotoff('Breuer');
+SELECT daitch_mokotoff('Freud');
+SELECT daitch_mokotoff('Haber');
+SELECT daitch_mokotoff('Manheim');
+SELECT daitch_mokotoff('Mintz');
+SELECT daitch_mokotoff('Topf');
+SELECT daitch_mokotoff('Kleinman');
+SELECT daitch_mokotoff('Ben Aron');
+
+SELECT daitch_mokotoff('AUERBACH');
+SELECT daitch_mokotoff('OHRBACH');
+SELECT daitch_mokotoff('LIPSHITZ');
+SELECT daitch_mokotoff('LIPPSZYC');
+SELECT daitch_mokotoff('LEWINSKY');
+SELECT daitch_mokotoff('LEVINSKI');
+SELECT daitch_mokotoff('SZLAMAWICZ');
+SELECT daitch_mokotoff('SHLAMOVITZ');
+
+
+-- https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+SELECT daitch_mokotoff('Tsenyuv');
+SELECT daitch_mokotoff('Holubica');
+SELECT daitch_mokotoff('Golubitsa');
+SELECT daitch_mokotoff('Przemysl');
+SELECT daitch_mokotoff('Pshemeshil');
+SELECT daitch_mokotoff('Rosochowaciec');
+SELECT daitch_mokotoff('Rosokhovatsets');
+
+
+-- https://familypedia.fandom.com/wiki/Daitch-Mokotoff_Soundex
+SELECT daitch_mokotoff('Peters');
+SELECT daitch_mokotoff('Peterson');
+SELECT daitch_mokotoff('Moskowitz');
+SELECT daitch_mokotoff('Moskovitz');
+SELECT daitch_mokotoff('Auerbach');
+SELECT daitch_mokotoff('Uhrbach');
+SELECT daitch_mokotoff('Jackson');
+SELECT daitch_mokotoff('Jackson-Jackson');
+
+
+-- Perl Text::Phonetic::DaitchMokotoff 006_daitchmokotoff.t
+-- Tests covered above are omitted.
+SELECT daitch_mokotoff('Müller');
+SELECT daitch_mokotoff('schmidt');
+SELECT daitch_mokotoff('schneider');
+SELECT daitch_mokotoff('fischer');
+SELECT daitch_mokotoff('weber');
+SELECT daitch_mokotoff('meyer');
+SELECT daitch_mokotoff('wagner');
+SELECT daitch_mokotoff('schulz');
+SELECT daitch_mokotoff('becker');
+SELECT daitch_mokotoff('hoffmann');
+SELECT daitch_mokotoff('schäfer');
+
+
+-- Apache Commons DaitchMokotoffSoundexTest.java
+
+-- testAccentedCharacterFolding
+SELECT daitch_mokotoff('Straßburg');
+SELECT daitch_mokotoff('Strasburg');
+
+SELECT daitch_mokotoff('Éregon');
+SELECT daitch_mokotoff('Eregon');
+
+-- testAdjacentCodes
+SELECT daitch_mokotoff('AKSSOL');
+SELECT daitch_mokotoff('GERSCHFELD');
+
+-- testEncodeBasic
+-- Tests covered above are omitted.
+
+-- testEncodeIgnoreApostrophes
+SELECT daitch_mokotoff('OBrien');
+SELECT daitch_mokotoff('''OBrien');
+SELECT daitch_mokotoff('O''Brien');
+SELECT daitch_mokotoff('OB''rien');
+SELECT daitch_mokotoff('OBr''ien');
+SELECT daitch_mokotoff('OBri''en');
+SELECT daitch_mokotoff('OBrie''n');
+SELECT daitch_mokotoff('OBrien''');
+
+-- testEncodeIgnoreHyphens
+SELECT daitch_mokotoff('KINGSMITH');
+SELECT daitch_mokotoff('-KINGSMITH');
+SELECT daitch_mokotoff('K-INGSMITH');
+SELECT daitch_mokotoff('KI-NGSMITH');
+SELECT daitch_mokotoff('KIN-GSMITH');
+SELECT daitch_mokotoff('KING-SMITH');
+SELECT daitch_mokotoff('KINGS-MITH');
+SELECT daitch_mokotoff('KINGSM-ITH');
+SELECT daitch_mokotoff('KINGSMI-TH');
+SELECT daitch_mokotoff('KINGSMIT-H');
+SELECT daitch_mokotoff('KINGSMITH-');
+
+-- testEncodeIgnoreTrimmable
+SELECT daitch_mokotoff(E' \t\n\r Washington \t\n\r ');
+SELECT daitch_mokotoff('Washington');
+
+-- testSoundexBasic
+-- Tests covered above are omitted.
+
+-- testSoundexBasic2
+-- Tests covered above are omitted.
+
+-- testSoundexBasic3
+-- Tests covered above are omitted.
+
+-- testSpecialRomanianCharacters
+SELECT daitch_mokotoff('ţamas'); -- t-cedila
+SELECT daitch_mokotoff('țamas'); -- t-comma
+
+
+-- Contrived case which is not handled correctly by other implementations.
+SELECT daitch_mokotoff('CJC');
diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml
index d3ca4b6932..0788db060d 100644
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@@ -105,6 +105,7 @@ CREATE EXTENSION <replaceable>module_name</replaceable>;
  &citext;
  &cube;
  &dblink;
+ &daitch-mokotoff;
  &dict-int;
  &dict-xsyn;
  &earthdistance;
diff --git a/doc/src/sgml/daitch-mokotoff.sgml b/doc/src/sgml/daitch-mokotoff.sgml
new file mode 100644
index 0000000000..6dbc817eca
--- /dev/null
+++ b/doc/src/sgml/daitch-mokotoff.sgml
@@ -0,0 +1,92 @@
+<!-- doc/src/sgml/daitch-mokotoff.sgml -->
+
+<sect1 id="daitch-mokotoff" xreflabel="daitch_mokotoff">
+ <title>daitch_mokotoff</title>
+
+ <indexterm zone="daitch-mokotoff">
+  <primary>daitch_mokotoff</primary>
+ </indexterm>
+
+ <para>
+  The <filename>daitch_mokotoff</filename> module provides an implementation
+  of the Daitch-Mokotoff Soundex System.
+ </para>
+
+ <para>
+  Compared to the American Soundex System implemented in
+  the <filename>fuzzystrmatch</filename> module, the major improvements of the
+  Daitch-Mokotoff Soundex System are:
+
+  <itemizedlist spacing="compact" mark="bullet">
+   <listitem>
+    <para>
+     Information is coded to the first six meaningful letters rather than
+     four.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     The initial letter is coded rather than kept as is.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     Where two consecutive letters have a single sound, they are coded as a
+     single number.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     When a letter or combination of letters may have two different sounds,
+     it is double coded under the two different codes.
+    </para>
+   </listitem>
+   <listitem>
+    <para>
+     A letter or combination of letters maps into ten possible codes rather
+     than seven.
+    </para>
+   </listitem>
+  </itemizedlist>
+
+  The <function>daitch_mokotoff</function> function shown in
+  <xref linkend="functions-daitch-mokotoff-table"/> generates Daitch-Mokotoff
+  soundex codes for matching of similar-sounding names.
+ </para>
+
+ <table id="functions-daitch-mokotoff-table">
+  <title><filename>daitch_mokotoff</filename> Functions</title>
+    <tgroup cols="1">
+     <thead>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        Function
+       </para>
+       <para>
+        Description
+       </para></entry>
+      </row>
+     </thead>
+
+     <tbody>
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <function>daitch_mokotoff</function> ( <parameter>name</parameter> <type>text</type> )
+        <returnvalue>text</returnvalue>
+       </para>
+       <para>
+        Generates Daitch-Mokotoff soundex codes.
+       </para></entry>
+      </row>
+     </tbody>
+  </tgroup>
+ </table>
+
+ <indexterm>
+  <primary>daitch_mokotoff</primary>
+ </indexterm>
+ <para>
+  <function>daitch_mokotoff</function> generates Daitch-Mokotoff soundex codes for the specified <parameter>name</parameter>. Since alternate soundex codes are separated by spaces, the returned text is suited for use in Full Text Search, see <xref linkend="textsearch"/>.
+ </para>
+
+</sect1>
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 89454e99b9..9ac43e5928 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -117,6 +117,7 @@
 <!ENTITY btree-gist      SYSTEM "btree-gist.sgml">
 <!ENTITY citext          SYSTEM "citext.sgml">
 <!ENTITY cube            SYSTEM "cube.sgml">
+<!ENTITY daitch-mokotoff SYSTEM "daitch-mokotoff.sgml">
 <!ENTITY dblink          SYSTEM "dblink.sgml">
 <!ENTITY dict-int        SYSTEM "dict-int.sgml">
 <!ENTITY dict-xsyn       SYSTEM "dict-xsyn.sgml">

---

From: Dag Lem <[email-masked]>
Date: Mon, 13 Dec 2021 14:38:22 +0100

Please find attached an updated patch, with the following fixes:

* Replaced remaining malloc/free with palloc/pfree.
* Made "make check" pass.
* Updated notes on other implementations.

Best regards

Dag Lem

index 0000000000..a7f1fd8541
@@ -0,0 +1,549 @@
+ * https://stevemorse.org/census/soundex.html (dmlat.php, dmsoundex.php)
+ * - Identical code digits for adjacent letters are not collapsed correctly in
+ *   dmsoundex.php when double digit codes are involved. E.g. "BESST" yields
+ *   744300 instead of 743000 as for "BEST".
+ * - No other known implementation yields the correct set of codes for e.g.
+void *
+palloc(size_t size)
+	void	   *ptr;
+	ptr = malloc(size);
+	if (ptr == NULL)
+		fprintf(stderr, "Unable to allocate memory\n");
+		exit(EXIT_FAILURE);
+	return ptr;
+#define pfree free
+	_daitch_mokotoff(string, tmp_soundex, DM_MAX_SOUNDEX_CHARS);
+	dm_node    *nodes = palloc(sizeof(dm_nodes));
+	dm_leaves  *leaves = palloc(2 * sizeof(dm_leaves));
+	pfree(leaves);
+	pfree(nodes);
+	soundex = palloc(DM_MAX_SOUNDEX_CHARS);
+	_daitch_mokotoff(argv[1], soundex, DM_MAX_SOUNDEX_CHARS);
+	pfree(soundex);
index 0000000000..57825aeb99
@@ -0,0 +1,472 @@

---

From: Tomas Vondra <[email-masked]>
Date: Mon, 13 Dec 2021 15:26:44 +0100

> * Updated notes on other implementations.

Thanks, looks interesting. A couple generic comments, based on a quick 
code review.

1) Can the extension be marked as trusted, just like fuzzystrmatch?

2) The docs really need an explanation of what the extension is for, not 
just a link to fuzzystrmatch. Also, a couple examples would be helpful, 
I guess - similarly to fuzzystrmatch. The last line in the docs is 
annoyingly long.

3) What's daitch_mokotov_header.pl for? I mean, it generates the header, 
but when do we need to run it?

4) It seems to require perl-open, which is a module we did not need 
until now. Not sure how well supported it is, but maybe we can use a 
more standard module?

5) Do we need to keep DM_MAIN? It seems to be meant for some kind of 
testing, but our regression tests certainly don't need it (or the palloc 
mockup). I suggest to get rid of it.

6) I really don't understand some of the comments in daitch_mokotov.sql, 
like for example:

-- testEncodeBasic
-- Tests covered above are omitted.

Also, comments with names of Java methods seem pretty confusing. It'd be 
better to actually explain what rules are the tests checking.

7) There are almost no comments in the .c file (ignoring the comment on 
top). Short functions like initialize_node are probably fine without 
one, but e.g. update_node would deserve one.

8) Some of the lines are pretty long (e.g. the update_node signature is 
almost 170 chars). That should be wrapped. Maybe try running pgindent on 
the code, that'll show which parts need better formatting (so as not to 
get broken later).

9) I'm sure there's better way to get the number of valid chars than this:

   for (i = 0, ilen = 0; (c = read_char(&str[i], &ilen)) && (c < 'A' || 
c > ']'); i += ilen)
   {
   }

Say, a while loop or something?

regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

---

From: Andrew Dunstan <[email-masked]>
Date: Mon, 13 Dec 2021 10:05:35 -0500

On 12/13/21 09:26, Tomas Vondra wrote:
> 2) The docs really need an explanation of what the extension is for,
> not just a link to fuzzystrmatch. Also, a couple examples would be
> helpful, I guess - similarly to fuzzystrmatch. The last line in the
> docs is annoyingly long.

It's not clear to me why we need a new module for this. Wouldn't it be
better just to add the new function to fuzzystrmatch?

cheers

andrew

--
Andrew Dunstan
EDB: https://www.enterprisedb.com

---

From: Tomas Vondra <[email-masked]>
Date: Mon, 13 Dec 2021 17:18:07 +0100

> better just to add the new function to fuzzystrmatch?

Yeah, that's a valid point. I think we're quite conservative about 
adding more contrib modules, and adding a function to an existing one 
works around a lot of that.

regards

---

From: Dag Lem <[email-masked]>
Date: Tue, 14 Dec 2021 23:34:00 +0100

Tomas Vondra <[email-masked]> writes:

[...]

> Thanks, looks interesting. A couple generic comments, based on a quick

Thank you for the constructive review!

> 1) Can the extension be marked as trusted, just like fuzzystrmatch?

I have now moved the daitch_mokotoff function into the fuzzystrmatch
module, as suggested by Andrew Dunstan.

> helpful, I guess - similarly to fuzzystrmatch. The last line in the

Please see the updated documentation for the fuzzystrmatch module.

>
> 3) What's daitch_mokotov_header.pl for? I mean, it generates the
> header, but when do we need to run it?

It only has to be run if the soundex rules are changed. I have now
made the dependencies explicit in the fuzzystrmatch Makefile.

> until now. Not sure how well supported it is, but maybe we can use a

I believe Perl I/O layers have been part of Perl core for two decades
now :-)

> testing, but our regression tests certainly don't need it (or the
> palloc mockup). I suggest to get rid of it.

Done. BTW this was modeled after dmetaphone.c

>
> 6) I really don't understand some of the comments in
> daitch_mokotov.sql, like for example:
>
> -- testEncodeBasic
> Also, comments with names of Java methods seem pretty confusing. It'd
> be better to actually explain what rules are the tests checking.

The tests were copied from various web sites and implementations. I have
cut down on the number of tests and made the comments more to the point.

>
> 7) There are almost no comments in the .c file (ignoring the comment
> on top). Short functions like initialize_node are probably fine
> without one, but e.g. update_node would deserve one.

More comments are added to both the .h and the .c file.

>
> 8) Some of the lines are pretty long (e.g. the update_node signature
> is almost 170 chars). That should be wrapped. Maybe try running
> pgindent on the code, that'll show which parts need better formatting
> (so as not to get broken later).

Fixed. I did run pgindent earlier, however it didn't catch those long
lines.

> Say, a while loop or something?

The code gets to the next encodable character, skipping any other
characters. I have now added a comment which should hopefully make this
clearer, and broken up the for loop for readability.

Please find attached the revised patch.

Best regards

Dag Lem

diff --git a/contrib/fuzzystrmatch/Makefile b/contrib/fuzzystrmatch/Makefile
index 0704894f88..826e529e3e 100644
--- a/contrib/fuzzystrmatch/Makefile
+++ b/contrib/fuzzystrmatch/Makefile
@@ -3,11 +3,12 @@
 MODULE_big = fuzzystrmatch
 OBJS = \
 	$(WIN32RES) \
+	daitch_mokotoff.o \
 	dmetaphone.o \
 	fuzzystrmatch.o
 
 EXTENSION = fuzzystrmatch
-DATA = fuzzystrmatch--1.1.sql fuzzystrmatch--1.0--1.1.sql
+DATA = fuzzystrmatch--1.2.sql fuzzystrmatch--1.1--1.2.sql fuzzystrmatch--1.0--1.1.sql
 PGFILEDESC = "fuzzystrmatch - similarities and distance between strings"
 
 REGRESS = fuzzystrmatch
@@ -22,3 +23,8 @@ top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
+
+daitch_mokotoff.o: daitch_mokotoff.h
+
+daitch_mokotoff.h: daitch_mokotoff_header.pl
+	perl $< > $@
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff.c b/contrib/fuzzystrmatch/daitch_mokotoff.c
new file mode 100644
index 0000000000..302e9a6d86
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff.c
@@ -0,0 +1,516 @@
+/*
+/* Template for new node in soundex code tree */
+/* Initialize soundex code tree node for next code digit */
+/* Update soundex code tree node with next code digit */
+/* Mark soundex code tree node as leaf (soundex code completed) */
+/* Find next node corresponding to code digit, or create a new node */
+static dm_node * find_or_create_node(dm_nodes nodes, int *num_nodes,
+									 dm_node * node, char code_digit)
+/* Update node for next code digit(s) */
+update_node(dm_nodes nodes, dm_node * node, int *num_nodes,
+			dm_leaves leaves_next, int *num_leaves_next,
+			int char_number, char next_code_digit, char next_code_digit_2)
+			update_node(nodes, dirty_nodes[i], num_nodes,
+						leaves_next, num_leaves_next,
+						char_number, next_code_digit_2, '\0');
+/* Mark completed soundex node leaves. Return 1 when all nodes are completed */
+update_leaves(dm_nodes nodes, int *num_nodes,
+			  dm_leaves leaves[2], int *ix_leaves, int *num_leaves,
+			  int char_number, dm_codes codes)
+			if (update_node(nodes, node, num_nodes,
+							leaves[ix_leaves_next], &num_leaves_next,
+							char_number, code[0], code[1]))
+/* Mapping from ISO8859-1 to ASCII */
+/* Return next character, converted from UTF-8 to uppercase ASCII */
+/* Return next character in the character set [A..\]], skipping any other characters */
+	for (i = 0, ilen = 0;
+		 (c = read_char(&str[i], &ilen)) && (c < 'A' || c > ']');
+		 i += ilen)
+/* Generate all Daitch-Mokotoff soundex codes for word, separated by space */
+		for (j = i + ilen;
+			 (letters = letter->letters) && (c = read_valid_char(&word[j], &jlen));
+			 j += jlen)
+		if (update_leaves(nodes, &num_nodes,
+						  leaves, &ix_leaves, &num_leaves,
+						  i, codes))
+	for (i = 0, j = 0;
+		 i < num_leaves && j + DM_MAX_CODE_DIGITS + 1 <= n;
+		 i++, j += DM_MAX_CODE_DIGITS + 1)
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff.h b/contrib/fuzzystrmatch/daitch_mokotoff.h
index 0000000000..071760495c
+++ b/contrib/fuzzystrmatch/daitch_mokotoff.h
@@ -0,0 +1,1115 @@
+/* Letter in input sequence */
+	char		letter;			/* Present letter in sequence */
+	struct dm_letter *letters;	/* List of possible successive letters */
+	dm_codes   *codes;			/* Code sequence(s) for complete sequence */
+/* Node in soundex code tree */
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_MAX_CODE_DIGITS + 1];	/* Soundex code */
+	int			is_leaf;		/* Completed soundex codes are leaves */
+	int			last_update;	/* Character index for last update of node */
+	char		code_digit;		/* Current code digit */
+	/* Branching nodes */
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+/* Coding for alternative following letters in sequence. */
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff_header.pl b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
index 0000000000..30cf9d3909
+++ b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
@@ -0,0 +1,281 @@
+/* Letter in input sequence */
+	char		letter;			/* Present letter in sequence */
+	struct dm_letter *letters;	/* List of possible successive letters */
+	dm_codes   *codes;			/* Code sequence(s) for complete sequence */
+/* Node in soundex code tree */
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_MAX_CODE_DIGITS + 1];	/* Soundex code */
+	int			is_leaf;		/* Completed soundex codes are leaves */
+	int			last_update;	/* Character index for last update of node */
+	char		code_digit;		/* Current code digit */
+	/* Branching nodes */
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+/* Coding for alternative following letters in sequence. */
diff --git a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
index 493c95cdfa..1f7708fff0 100644
--- a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
+++ b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
@@ -65,3 +65,194 @@ SELECT dmetaphone_alt('gumbo');
  KMP
 (1 row)
 
+-- Wovels
+SELECT daitch_mokotoff('Augsburg');
+ daitch_mokotoff 
+-----------------
+ 054795
+(1 row)
+
+SELECT daitch_mokotoff('Breuer');
+ daitch_mokotoff 
+-----------------
+ 791900
+(1 row)
+
+SELECT daitch_mokotoff('Freud');
+ daitch_mokotoff 
+-----------------
+ 793000
+(1 row)
+
+-- The letter "H"
+SELECT daitch_mokotoff('Halberstadt');
+ daitch_mokotoff 
+-----------------
+ 587943 587433
+(1 row)
+
+SELECT daitch_mokotoff('Mannheim');
+ daitch_mokotoff 
+-----------------
+ 665600
+(1 row)
+
+-- Adjacent sounds
+SELECT daitch_mokotoff('Chernowitz');
+ daitch_mokotoff 
+-----------------
+ 596740 496740
+(1 row)
+
+-- Adjacent letters with identical adjacent code digits
+SELECT daitch_mokotoff('Cherkassy');
+ daitch_mokotoff 
+-----------------
+ 595400 495400
+(1 row)
+
+SELECT daitch_mokotoff('Kleinman');
+ daitch_mokotoff 
+-----------------
+ 586660
+(1 row)
+
+SELECT daitch_mokotoff('Besst');
+ daitch_mokotoff 
+-----------------
+ 743000
+(1 row)
+
+-- More than one word
+SELECT daitch_mokotoff('Nowy Targ');
+ daitch_mokotoff 
+-----------------
+ 673950
+(1 row)
+
+-- Padded with "0"
+SELECT daitch_mokotoff('Berlin');
+ daitch_mokotoff 
+-----------------
+ 798600
+(1 row)
+
+-- Other examples from https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+ daitch_mokotoff 
+-----------------
+ 567000 467000
+(1 row)
+
+SELECT daitch_mokotoff('Tsenyuv');
+ daitch_mokotoff 
+-----------------
+ 467000
+(1 row)
+
+SELECT daitch_mokotoff('Holubica');
+ daitch_mokotoff 
+-----------------
+ 587500 587400
+(1 row)
+
+SELECT daitch_mokotoff('Golubitsa');
+ daitch_mokotoff 
+-----------------
+ 587400
+(1 row)
+
+SELECT daitch_mokotoff('Przemysl');
+ daitch_mokotoff 
+-----------------
+ 794648 746480
+(1 row)
+
+SELECT daitch_mokotoff('Pshemeshil');
+ daitch_mokotoff 
+-----------------
+ 746480
+(1 row)
+
+SELECT daitch_mokotoff('Rosochowaciec');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 945755 945754 945745 945744 944755 944754 944745 944744
+(1 row)
+
+SELECT daitch_mokotoff('Rosokhovatsets');
+ daitch_mokotoff 
+-----------------
+ 945744
+(1 row)
+
+-- Accents
+SELECT daitch_mokotoff('Müller');
+ daitch_mokotoff 
+-----------------
+ 689000
+(1 row)
+
+SELECT daitch_mokotoff('Schäfer');
+ daitch_mokotoff 
+-----------------
+ 479000
+(1 row)
+
+SELECT daitch_mokotoff('Straßburg');
+ daitch_mokotoff 
+-----------------
+ 294795
+(1 row)
+
+SELECT daitch_mokotoff('Éregon');
+ daitch_mokotoff 
+-----------------
+ 095600
+(1 row)
+
+-- Ignored characters
+SELECT daitch_mokotoff('''OBrien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('O''Brien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+-- Special characters added at https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('gąszczu');
+ daitch_mokotoff 
+-----------------
+ 564000 540000
+(1 row)
+
+SELECT daitch_mokotoff('brzęczy');
+       daitch_mokotoff       
+-----------------------------
+ 794640 794400 746400 744000
+(1 row)
+
+SELECT daitch_mokotoff('ţamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
+SELECT daitch_mokotoff('țamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
+-- Contrived case which is not handled correctly by other implementations.
+SELECT daitch_mokotoff('CJC');
+              daitch_mokotoff              
+-------------------------------------------
+ 550000 540000 545000 450000 400000 440000
+(1 row)
+
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql b/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql
new file mode 100644
index 0000000000..b9d7b229a3
--- /dev/null
+++ b/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql
@@ -0,0 +1,8 @@
+/* contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION fuzzystrmatch UPDATE TO '1.2'" to load this file. \quit
+
+CREATE FUNCTION daitch_mokotoff(text) RETURNS text
+AS 'MODULE_PATHNAME', 'daitch_mokotoff'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch--1.1.sql b/contrib/fuzzystrmatch/fuzzystrmatch--1.2.sql
similarity index 92%
rename from contrib/fuzzystrmatch/fuzzystrmatch--1.1.sql
rename to contrib/fuzzystrmatch/fuzzystrmatch--1.2.sql
index 41de9d949b..2a8a100699 100644
--- a/contrib/fuzzystrmatch/fuzzystrmatch--1.1.sql
+++ b/contrib/fuzzystrmatch/fuzzystrmatch--1.2.sql
@@ -42,3 +42,7 @@ LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 CREATE FUNCTION dmetaphone_alt (text) RETURNS text
 AS 'MODULE_PATHNAME', 'dmetaphone_alt'
 LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+CREATE FUNCTION daitch_mokotoff(text) RETURNS text
+AS 'MODULE_PATHNAME', 'daitch_mokotoff'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch.control b/contrib/fuzzystrmatch/fuzzystrmatch.control
index 3cd6660bf9..8b6e9fd993 100644
--- a/contrib/fuzzystrmatch/fuzzystrmatch.control
+++ b/contrib/fuzzystrmatch/fuzzystrmatch.control
@@ -1,6 +1,6 @@
 # fuzzystrmatch extension
 comment = 'determine similarities and distance between strings'
-default_version = '1.1'
+default_version = '1.2'
 module_pathname = '$libdir/fuzzystrmatch'
 relocatable = true
 trusted = true
diff --git a/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql b/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
index f05dc28ffb..85ac755ddd 100644
--- a/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
+++ b/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
@@ -19,3 +19,55 @@ SELECT metaphone('GUMBO', 4);
 
 SELECT dmetaphone('gumbo');
 SELECT dmetaphone_alt('gumbo');
+
+-- Wovels
+SELECT daitch_mokotoff('Augsburg');
+SELECT daitch_mokotoff('Breuer');
+SELECT daitch_mokotoff('Freud');
+
+-- The letter "H"
+SELECT daitch_mokotoff('Halberstadt');
+SELECT daitch_mokotoff('Mannheim');
+
+-- Adjacent sounds
+SELECT daitch_mokotoff('Chernowitz');
+
+-- Adjacent letters with identical adjacent code digits
+SELECT daitch_mokotoff('Cherkassy');
+SELECT daitch_mokotoff('Kleinman');
+SELECT daitch_mokotoff('Besst');
+
+-- More than one word
+SELECT daitch_mokotoff('Nowy Targ');
+
+-- Padded with "0"
+SELECT daitch_mokotoff('Berlin');
+
+-- Other examples from https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+SELECT daitch_mokotoff('Tsenyuv');
+SELECT daitch_mokotoff('Holubica');
+SELECT daitch_mokotoff('Golubitsa');
+SELECT daitch_mokotoff('Przemysl');
+SELECT daitch_mokotoff('Pshemeshil');
+SELECT daitch_mokotoff('Rosochowaciec');
+SELECT daitch_mokotoff('Rosokhovatsets');
+
+-- Accents
+SELECT daitch_mokotoff('Müller');
+SELECT daitch_mokotoff('Schäfer');
+SELECT daitch_mokotoff('Straßburg');
+SELECT daitch_mokotoff('Éregon');
+
+-- Ignored characters
+SELECT daitch_mokotoff('''OBrien');
+SELECT daitch_mokotoff('O''Brien');
+
+-- Special characters added at https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('gąszczu');
+SELECT daitch_mokotoff('brzęczy');
+SELECT daitch_mokotoff('ţamas');
+SELECT daitch_mokotoff('țamas');
+
+-- Contrived case which is not handled correctly by other implementations.
+SELECT daitch_mokotoff('CJC');
diff --git a/doc/src/sgml/fuzzystrmatch.sgml b/doc/src/sgml/fuzzystrmatch.sgml
index 382e54be91..a5dbd535f4 100644
--- a/doc/src/sgml/fuzzystrmatch.sgml
+++ b/doc/src/sgml/fuzzystrmatch.sgml
@@ -241,4 +241,98 @@ test=# SELECT dmetaphone('gumbo');
 </screen>
  </sect2>
 
+ <sect2>
+  <title>Daitch-Mokotoff Soundex</title>
+
+  <para>
+   Compared to the American Soundex System implemented in the
+   <function>soundex</function> function, the major improvements of the
+   Daitch-Mokotoff Soundex System are:
+
+   <itemizedlist spacing="compact" mark="bullet">
+    <listitem>
+     <para>
+      Information is coded to the first six meaningful letters rather than
+      four.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      The initial letter is coded rather than kept as is.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      Where two consecutive letters have a single sound, they are coded as a
+      single number.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      When a letter or combination of letters may have two different sounds,
+      it is double coded under the two different codes.
+     </para>
+    </listitem>
+    <listitem>
+     <para>
+      A letter or combination of letters maps into ten possible codes rather
+      than seven.
+     </para>
+    </listitem>
+   </itemizedlist>
+  </para>
+
+  <indexterm>
+   <primary>daitch_mokotoff</primary>
+  </indexterm>
+
+  <para>
+   The following function generates Daitch-Mokotoff soundex codes for matching
+   of similar-sounding input:
+  </para>
+
+<synopsis>
+daitch_mokotoff(text source) returns text
+</synopsis>
+
+  <para>
+   Since a Daitch-Mokotoff soundex code consists of only 6 digits,
+   <literal>source</literal> should be preferably a single word or name.
+   Any alternative soundex codes are separated by space, which makes the returned
+   text suited for use in Full Text Search, see <xref linkend="textsearch"/> and
+   <xref linkend="functions-textsearch"/>.
+  </para>
+
+  <para>
+   Example:
+  </para>
+
+<programlisting>
+CREATE OR REPLACE FUNCTION soundex_name(v_name text) RETURNS text AS $$
+  SELECT string_agg(daitch_mokotoff(n), ' ')
+  FROM regexp_split_to_table(v_name, '\s+') AS n
+$$ LANGUAGE sql STRICT IMMUTABLE PARALLEL SAFE;
+
+CREATE OR REPLACE FUNCTION soundex_tsvector(v_name text) RETURNS tsvector AS $$
+  SELECT to_tsvector('simple', soundex_name(v_name))
+$$ LANGUAGE sql STRICT IMMUTABLE PARALLEL SAFE;
+
+CREATE OR REPLACE FUNCTION soundex_tsquery(v_name text) RETURNS tsquery AS $$
+  SELECT to_tsquery('simple', quote_literal(soundex_name(v_name)))
+$$ LANGUAGE sql STRICT IMMUTABLE PARALLEL SAFE;
+
+-- Note that searches could be more efficient with the tsvector in a separate column
+-- (no computation on table row recheck).
+CREATE TABLE s (nm text);
+CREATE INDEX ix_s_txt ON s USING gin (soundex_tsvector(nm)) WITH (fastupdate = off);
+
+INSERT INTO s VALUES ('john');
+INSERT INTO s VALUES ('joan');
+INSERT INTO s VALUES ('wobbly');
+INSERT INTO s VALUES ('jack');
+
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('john');
+</programlisting>
+ </sect2>
+
 </sect1>

---

From: Dag Lem <[email-masked]>
Date: Tue, 21 Dec 2021 22:41:18 +0100

Hello again,

It turns out that there actually exists an(other) implementation of
the Daitch-Mokotoff Soundex System which gets it right; the JOS
Soundex Calculator at https://www.jewishgen.org/jos/jossound.htm
Other implementations I have been able to find, like the one in Apache
Commons Coded used in e.g. Elasticsearch, are far from correct.

The source code for the JOS Soundex Calculator is not available, as
far as I can tell, however I have run the complete list of 98412 last
names at
https://raw.githubusercontent.com/philipperemy/name-dataset/master/names_dataset/v1/last_names.all.txt
through the calculator, in order to have a good basis for comparison.

This revealed a few shortcomings in my implementation. In particular I
had to go back to the drawing board in order to handle the dual nature
of "J" correctly. "J" can be either a vowel or a consonant in
Daitch-Mokotoff soundex, and this complicates encoding of the
*previous* character.

I have also done a more thorough review and refactoring of the code,
which should hopefully make things quite a bit more understandable to
others.

The changes are summarized as follows:

* Returns NULL for input without any encodable characters.
* Uses the same "unoffical" rules for "UE" as other implementations.
* Correctly considers "J" as either a vowel or a consonant.
* Corrected encoding for e.g. "HANNMANN".
* Code refactoring and comments for readability.
* Better examples in the documentation.

The implementation is now in correspondence with the JOS Soundex
Calculator for the 98412 last names mentioned above, with only the
following exceptions:

JOS: cedeño 430000 530000
PG:  cedeño 436000 536000
JOS: sadab(khura)  437000
PG:  sadab(khura)  437590

I hope this addition to the fuzzystrmatch extension module will prove
to be useful to others as well!

This is my very first code contribution to PostgreSQL, and I would be
grateful for any advice on how to proceed in order to get the patch
accepted.

Best regards

Dag Lem

 
 REGRESS = fuzzystrmatch
@@ -22,3 +23,8 @@ top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
+
+daitch_mokotoff.o: daitch_mokotoff.h
+
+daitch_mokotoff.h: daitch_mokotoff_header.pl
+	perl $< > $@
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff.c b/contrib/fuzzystrmatch/daitch_mokotoff.c
new file mode 100644
index 0000000000..1b7263c349
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff.c
@@ -0,0 +1,593 @@
+/*
+ * Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <[email-masked]>
+ *
+ * This implementation of the Daitch-Mokotoff Soundex System aims at high
+ * performance.
+ *
+ * - The processing of each phoneme is initiated by an O(1) table lookup.
+ * - For phonemes containing more than one character, a coding tree is traversed
+ *   to process the complete phoneme.
+ * - The (alternate) soundex codes are produced digit by digit in-place in
+ *   another tree structure.
+ *
+ *  References:
+ *
+ * https://www.avotaynu.com/soundex.htm
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * https://familypedia.fandom.com/wiki/Daitch-Mokotoff_Soundex
+ * https://stevemorse.org/census/soundex.html (dmlat.php, dmsoundex.php)
+ * https://github.com/apache/commons-codec/ (dmrules.txt, DaitchMokotoffSoundex.java)
+ * https://metacpan.org/pod/Text::Phonetic (DaitchMokotoff.pm)
+ *
+ * A few notes on other implementations:
+ *
+ * - All other known implementations have the same unofficial rules for "UE",
+ *   these are also adapted by this implementation (0, 1, NC).
+ * - The only other known implementation which is capable of generating all
+ *   correct soundex codes in all cases is the JOS Soundex Calculator at
+ *   https://www.jewishgen.org/jos/jossound.htm
+ * - "J" is considered (only) a vowel in dmlat.php
+ * - The official rules for "RS" are commented out in dmlat.php
+ * - Identical code digits for adjacent letters are not collapsed correctly in
+ *   dmsoundex.php when double digit codes are involved. E.g. "BESST" yields
+ *   744300 instead of 743000 as for "BEST".
+ * - "J" is considered (only) a consonant in DaitchMokotoffSoundex.java
+ * - "Y" is not considered a vowel in DaitchMokotoffSoundex.java
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+*/
+
+#include "daitch_mokotoff.h"
+
+#include "postgres.h"
+#include "utils/builtins.h"
+#include "mb/pg_wchar.h"
+
+#include <ctype.h>
+#include <string.h>
+
+/* Internal C implementation */
+static char *_daitch_mokotoff(char *word, char *soundex, size_t n);
+
+
+PG_FUNCTION_INFO_V1(daitch_mokotoff);
+Datum
+daitch_mokotoff(PG_FUNCTION_ARGS)
+{
+	text	   *arg = PG_GETARG_TEXT_PP(0);
+	char	   *string,
+			   *tmp_soundex;
+	text	   *soundex;
+
+	/*
+	 * The maximum theoretical soundex size is several KB, however in practice
+	 * anything but contrived synthetic inputs will yield a soundex size of
+	 * less than 100 bytes. We thus allocate and free a temporary work buffer,
+	 * and return only the actual soundex result.
+	 */
+	string = pg_server_to_any(text_to_cstring(arg), VARSIZE_ANY_EXHDR(arg), PG_UTF8);
+	tmp_soundex = palloc(DM_MAX_SOUNDEX_CHARS);
+
+	if (!_daitch_mokotoff(string, tmp_soundex, DM_MAX_SOUNDEX_CHARS))
+	{
+		/* No encodable characters in input. */
+		pfree(tmp_soundex);
+		PG_RETURN_NULL();
+	}
+
+	soundex = cstring_to_text(pg_any_to_server(tmp_soundex, strlen(tmp_soundex), PG_UTF8));
+	pfree(tmp_soundex);
+
+	PG_RETURN_TEXT_P(soundex);
+}
+
+
+typedef dm_node dm_nodes[DM_MAX_NODES];
+typedef dm_node * dm_leaves[DM_MAX_LEAVES];
+
+
+/* Template for new node in soundex code tree. */
+static const dm_node start_node = {
+	.soundex_length = 0,
+	.soundex = "000000 ",		/* Six digits + joining space */
+	.is_leaf = 0,
+	.last_update = 0,
+	.code_digit = '\0',
+	.prev_code_digits = {'\0', '\0'},
+	.next_code_digits = {'\0', '\0'},
+	.prev_code_index = 0,
+	.next_code_index = 0,
+	.next_nodes = {NULL}
+};
+
+/* Dummy soundex codes at end of input. */
+static dm_codes end_codes[2] =
+{
+	{
+		"X", "X", "X"
+	}
+};
+
+
+/* Initialize soundex code tree node for next code digit. */
+static void
+initialize_node(dm_node * node, int last_update)
+{
+	if (node->last_update < last_update)
+	{
+		node->prev_code_digits[0] = node->next_code_digits[0];
+		node->prev_code_digits[1] = node->next_code_digits[1];
+		node->next_code_digits[0] = '\0';
+		node->next_code_digits[1] = '\0';
+		node->prev_code_index = node->next_code_index;
+		node->next_code_index = 0;
+		node->is_leaf = 0;
+		node->last_update = last_update;
+	}
+}
+
+
+/* Update soundex code tree node with next code digit. */
+static void
+add_next_code_digit(dm_node * node, int code_index, char code_digit)
+{
+	/* OR in index 1 or 2. */
+	node->next_code_index |= code_index;
+
+	if (!node->next_code_digits[0])
+	{
+		node->next_code_digits[0] = code_digit;
+	}
+	else if (node->next_code_digits[0] != code_digit)
+	{
+		node->next_code_digits[1] = code_digit;
+	}
+}
+
+
+/* Mark soundex code tree node as leaf. */
+static void
+set_leaf(dm_leaves leaves_next, int *num_leaves_next, dm_node * node)
+{
+	if (!node->is_leaf)
+	{
+		node->is_leaf = 1;
+		leaves_next[(*num_leaves_next)++] = node;
+	}
+}
+
+
+/* Find next node corresponding to code digit, or create a new node. */
+static dm_node * find_or_create_node(dm_nodes nodes, int *num_nodes,
+									 dm_node * node, char code_digit)
+{
+	dm_node   **next_nodes;
+	dm_node    *next_node;
+
+	for (next_nodes = node->next_nodes; (next_node = *next_nodes); next_nodes++)
+	{
+		if (next_node->code_digit == code_digit)
+		{
+			return next_node;
+		}
+	}
+
+	next_node = &nodes[(*num_nodes)++];
+	*next_nodes = next_node;
+
+	*next_node = start_node;
+	memcpy(next_node->soundex, node->soundex, sizeof(next_node->soundex));
+	next_node->soundex_length = node->soundex_length;
+	next_node->soundex[next_node->soundex_length++] = code_digit;
+	next_node->code_digit = code_digit;
+	next_node->next_code_index = node->prev_code_index;
+
+	return next_node;
+}
+
+
+/* Update node for next code digit(s). */
+static int
+update_node(dm_nodes nodes, dm_node * node, int *num_nodes,
+			dm_leaves leaves_next, int *num_leaves_next,
+			int letter_no, int prev_code_index, int next_code_index,
+			char *next_code_digits, int digit_no)
+{
+	int			i;
+	char		next_code_digit = next_code_digits[digit_no];
+	int			num_dirty_nodes = 0;
+	dm_node    *dirty_nodes[2];
+
+	initialize_node(node, letter_no);
+
+	if (node->soundex_length == DM_MAX_CODE_DIGITS)
+	{
+		/* Keep completed soundex code. */
+		set_leaf(leaves_next, num_leaves_next, node);
+		return 0;
+	}
+
+	if (node->prev_code_index && !(node->prev_code_index & prev_code_index))
+	{
+		/*
+		 * If the sound (vowel / consonant) of this letter encoding doesn't
+		 * correspond to the coding index of the previous letter, we skip this
+		 * letter encoding. Note that currently, only "J" can be either a
+		 * vowel or a consonant.
+		 */
+		return 1;
+	}
+
+	if (next_code_digit == 'X' ||
+		(digit_no == 0 &&
+		 (node->prev_code_digits[0] == next_code_digit ||
+		  node->prev_code_digits[1] == next_code_digit)))
+	{
+		/* The code digit is the same as one of the previous (i.e. not added). */
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	if (next_code_digit != 'X' &&
+		(digit_no > 0 ||
+		 node->prev_code_digits[0] != next_code_digit ||
+		 node->prev_code_digits[1]))
+	{
+		/* The code digit is different from one of the previous (i.e. added). */
+		node = find_or_create_node(nodes, num_nodes, node, next_code_digit);
+		initialize_node(node, letter_no);
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	for (i = 0; i < num_dirty_nodes; i++)
+	{
+		/* Add code digit leading to the current node. */
+		add_next_code_digit(dirty_nodes[i], next_code_index, next_code_digit);
+
+		if (next_code_digits[++digit_no])
+		{
+			update_node(nodes, dirty_nodes[i], num_nodes,
+						leaves_next, num_leaves_next,
+						letter_no, prev_code_index, next_code_index,
+						next_code_digits, digit_no);
+		}
+		else
+		{
+			set_leaf(leaves_next, num_leaves_next, dirty_nodes[i]);
+		}
+	}
+
+	return 1;
+}
+
+
+/* Update soundex tree leaf nodes. Return 1 when all nodes are completed. */
+static int
+update_leaves(dm_nodes nodes, int *num_nodes,
+			  dm_leaves leaves[2], int *ix_leaves, int *num_leaves,
+			  int letter_no, dm_codes * codes, dm_codes * next_codes)
+{
+	int			i,
+				j,
+				k,
+				code_index;
+	dm_code    *code,
+			   *next_code;
+	int			num_leaves_next = 0;
+	int			ix_leaves_next = (*ix_leaves + 1) & 1;	/* Alternate ix: 0, 1 */
+	int			finished = 1;
+
+	for (i = 0; i < *num_leaves; i++)
+	{
+		dm_node    *node = leaves[*ix_leaves][i];
+
+		/* One or two alternate code sequences. */
+		for (j = 0; j < 2 && (code = codes[j]) && code[0][0]; j++)
+		{
+			/* Coding for previous letter - before vowel: 1, all other: 2 */
+			int			prev_code_index = (code[0][0] > '1') + 1;
+
+			/* One or two alternate next code sequences. */
+			for (k = 0; k < 2 && (next_code = next_codes[k]) && next_code[0][0]; k++)
+			{
+				/* Determine which code to use. */
+				if (letter_no == 0)
+				{
+					/* This is the first letter. */
+					code_index = 0;
+				}
+				else if (next_code[0][0] <= '1')
+				{
+					/* The next letter is a vowel. */
+					code_index = 1;
+				}
+				else
+				{
+					/* All other cases. */
+					code_index = 2;
+				}
+
+				/* One or two sequential code digits. */
+				if (update_node(nodes, node, num_nodes,
+								leaves[ix_leaves_next], &num_leaves_next,
+								letter_no, prev_code_index, code_index,
+								code[code_index], 0))
+				{
+					finished = 0;
+				}
+			}
+		}
+	}
+
+	*ix_leaves = ix_leaves_next;
+	*num_leaves = num_leaves_next;
+
+	return finished;
+}
+
+
+/* Mapping from ISO8859-1 to ASCII */
+static const char tr_accents_iso8859_1[] =
+/*
+"ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
+*/
+"AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDsaaaaaaeceeeeiiiidnooooo/ouuuuydy";
+
+static char
+unaccent_iso8859_1(unsigned char c)
+{
+	return c >= 192 ? tr_accents_iso8859_1[c - 192] : c;
+}
+
+
+/* Convert an UTF-8 character to ISO-8859-1.
+ * Unconvertable characters are returned as '?'.
+ * NB! Beware of the domain specific conversion of Ą, Ę, and Ţ/Ț.
+ */
+static char
+utf8_to_iso8859_1(char *str, int *ix)
+{
+	const char	unknown = '?';
+	unsigned char c,
+				c2;
+	unsigned int code_point;
+
+	/* First byte. */
+	c = (unsigned char) str[(*ix)++];
+	if (c < 0x80)
+	{
+		/* ASCII code point. */
+		if (c >= '[' && c <= ']')
+		{
+			/* Codes reserved for Ą, Ę, and Ţ/Ț. */
+			return unknown;
+		}
+
+		return c;
+	}
+
+	/* Second byte. */
+	c2 = (unsigned char) str[(*ix)++];
+	if (!c2)
+	{
+		/* The UTF-8 character is cut short (invalid code point). */
+		(*ix)--;
+		return unknown;
+	}
+
+	if (c < 0xE0)
+	{
+		/* Two-byte character. */
+		code_point = ((c & 0x1F) << 6) | (c2 & 0x3F);
+		if (code_point < 0x100)
+		{
+			/* ISO-8859-1 code point. */
+			return code_point;
+		}
+		else if (code_point == 0x0104 || code_point == 0x0105)
+		{
+			/* Ą/ą */
+			return '[';
+		}
+		else if (code_point == 0x0118 || code_point == 0x0119)
+		{
+			/* Ę/ę */
+			return '\\';
+		}
+		else if (code_point == 0x0162 || code_point == 0x0163 ||
+				 code_point == 0x021A || code_point == 0x021B)
+		{
+			/* Ţ/ţ or Ț/ț */
+			return ']';
+		}
+		else
+		{
+			return unknown;
+		}
+	}
+
+	/* Third byte. */
+	if (!str[(*ix)++])
+	{
+		/* The UTF-8 character is cut short (invalid code point). */
+		(*ix)--;
+		return unknown;
+	}
+
+	if (c < 0xF0)
+	{
+		/* Three-byte character. */
+		return unknown;
+	}
+
+	/* Fourth byte. */
+	if (!str[(*ix)++])
+	{
+		/* The UTF-8 character is cut short (invalid code point). */
+		(*ix)--;
+	}
+
+	return unknown;
+}
+
+
+/* Return next character, converted from UTF-8 to uppercase ASCII. */
+static char
+read_char(char *str, int *ix)
+{
+	return toupper(unaccent_iso8859_1(utf8_to_iso8859_1(str, ix)));
+}
+
+
+/* Convert input to ASCII, skipping any characters not in [A-\]]. */
+static void
+normalize_input(char *src, char *dst)
+{
+	int			c;
+	int			i = 0,
+				j = 0;
+
+	while ((c = read_char(src, &i)))
+	{
+		if (c >= 'A' && c <= ']')
+		{
+			dst[j++] = c;
+		}
+	}
+
+	dst[j] = '\0';
+}
+
+
+/* Return sound coding for "letter" (letter sequence) */
+static dm_codes *
+read_letter(char *str, int *ix)
+{
+	int			c,
+				cmp;
+	int			i = *ix,
+				j;
+	dm_letter  *letters;
+	dm_codes   *codes;
+
+	/* First letter in sequence. */
+	if (!(c = str[i++]))
+	{
+		return NULL;
+	}
+	letters = &letter_[c - 'A'];
+	codes = letters->codes;
+	*ix = i;
+
+	/* Any subsequent letters in sequence. */
+	while ((letters = letters->letters) && (c = str[i++]))
+	{
+		for (j = 0; (cmp = letters[j].letter); j++)
+		{
+			if (cmp == c)
+			{
+				/* Letter found. */
+				letters = &letters[j];
+				if (letters->codes)
+				{
+					/* Coding for letter sequence found. */
+					codes = letters->codes;
+					*ix = i;
+				}
+				break;
+			}
+		}
+		if (!cmp)
+		{
+			/* The sequence of letters has no coding. */
+			break;
+		}
+	}
+
+	return codes;
+}
+
+
+/* Generate all Daitch-Mokotoff soundex codes for word, separated by space. */
+static char *
+_daitch_mokotoff(char *word, char *soundex, size_t n)
+{
+	int			i = 0,
+				j;
+	int			letter_no = 0;
+	int			ix_leaves = 0;
+	int			num_nodes = 0,
+				num_leaves = 0;
+	dm_codes   *codes,
+			   *next_codes;
+	dm_node    *nodes;
+	dm_leaves  *leaves;
+
+	/* Convert input to encodable ASCII characters, stored in soundex buffer. */
+	normalize_input(word, soundex);
+	if (!soundex[0])
+	{
+		/* No encodable character in input. */
+		return NULL;
+	}
+
+	/* Allocate memory for node tree. */
+	nodes = palloc(sizeof(dm_nodes));
+	leaves = palloc(2 * sizeof(dm_leaves));
+
+	/* Starting point. */
+	nodes[num_nodes++] = start_node;
+	leaves[ix_leaves][num_leaves++] = &nodes[0];
+
+	codes = read_letter(soundex, &i);
+
+	while (codes)
+	{
+		next_codes = read_letter(soundex, &i);
+
+		/* Update leaf nodes. */
+		if (update_leaves(nodes, &num_nodes,
+						  leaves, &ix_leaves, &num_leaves,
+						  letter_no, codes, next_codes ? next_codes : end_codes))
+		{
+			/* All soundex codes are completed to six digits. */
+			break;
+		}
+
+		codes = next_codes;
+		letter_no++;
+	}
+
+	/* Concatenate all generated soundex codes. */
+	for (i = 0, j = 0;
+		 i < num_leaves && j + DM_MAX_CODE_DIGITS + 1 <= n;
+		 i++, j += DM_MAX_CODE_DIGITS + 1)
+	{
+		memcpy(&soundex[j], leaves[ix_leaves][i]->soundex, DM_MAX_CODE_DIGITS + 1);
+	}
+
+	/* Terminate string. */
+	soundex[j - (j != 0)] = '\0';
+
+	pfree(leaves);
+	pfree(nodes);
+
+	return soundex;
+}
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff.h b/contrib/fuzzystrmatch/daitch_mokotoff.h
new file mode 100644
index 0000000000..8426069825
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff.h
@@ -0,0 +1,999 @@
+/*
+ * Types and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <[email-masked]>
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include <stdlib.h>
+
+#define DM_MAX_CODE_DIGITS 6
+#define DM_MAX_ALTERNATE_CODES 5
+#define DM_MAX_NODES 1564
+#define DM_MAX_LEAVES 1250
+#define DM_MAX_SOUNDEX_CHARS (DM_MAX_NODES*(DM_MAX_CODE_DIGITS + 1))
+
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[3];	/* Start of name, before a vowel, any other */
+
+/* Letter in input sequence */
+struct dm_letter
+{
+	char		letter;			/* Present letter in sequence */
+	struct dm_letter *letters;	/* List of possible successive letters */
+	dm_codes   *codes;			/* Code sequence(s) for complete sequence */
+};
+
+/* Node in soundex code tree */
+struct dm_node
+{
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_MAX_CODE_DIGITS + 1];	/* Soundex code */
+	int			is_leaf;		/* Candidate for complete soundex code */
+	int			last_update;	/* Letter number for last update of node */
+	char		code_digit;		/* Last code digit, 0 - 9 */
+
+	/*
+	 * One or two alternate code digits leading to this node. If there are two
+	 * digits, one of them is always an 'X'. Repeated code digits and 'X' lead
+	 * back to the same node.
+	 */
+	char		prev_code_digits[2];
+	/* One or two alternate code digits moving forward. */
+	char		next_code_digits[2];
+	/* ORed together code index(es) used to reach current node. */
+	int			prev_code_index;
+	int			next_code_index;
+	/* Nodes branching out from this node. */
+	struct dm_node *next_nodes[DM_MAX_ALTERNATE_CODES + 1];
+};
+
+typedef struct dm_letter dm_letter;
+typedef struct dm_node dm_node;
+
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+static dm_codes codes_0_1_X[2] =
+{
+	{
+		"0", "1", "X"
+	}
+};
+static dm_codes codes_0_7_X[2] =
+{
+	{
+		"0", "7", "X"
+	}
+};
+static dm_codes codes_0_X_X[2] =
+{
+	{
+		"0", "X", "X"
+	}
+};
+static dm_codes codes_1_1_X[2] =
+{
+	{
+		"1", "1", "X"
+	}
+};
+static dm_codes codes_1_X_X[2] =
+{
+	{
+		"1", "X", "X"
+	}
+};
+static dm_codes codes_1_X_X_or_4_4_4[2] =
+{
+	{
+		"1", "X", "X"
+	},
+	{
+		"4", "4", "4"
+	}
+};
+static dm_codes codes_2_43_43[2] =
+{
+	{
+		"2", "43", "43"
+	}
+};
+static dm_codes codes_2_4_4[2] =
+{
+	{
+		"2", "4", "4"
+	}
+};
+static dm_codes codes_3_3_3[2] =
+{
+	{
+		"3", "3", "3"
+	}
+};
+static dm_codes codes_3_3_3_or_4_4_4[2] =
+{
+	{
+		"3", "3", "3"
+	},
+	{
+		"4", "4", "4"
+	}
+};
+static dm_codes codes_4_4_4[2] =
+{
+	{
+		"4", "4", "4"
+	}
+};
+static dm_codes codes_5_54_54[2] =
+{
+	{
+		"5", "54", "54"
+	}
+};
+static dm_codes codes_5_5_5[2] =
+{
+	{
+		"5", "5", "5"
+	}
+};
+static dm_codes codes_5_5_5_or_45_45_45[2] =
+{
+	{
+		"5", "5", "5"
+	},
+	{
+		"45", "45", "45"
+	}
+};
+static dm_codes codes_5_5_5_or_4_4_4[2] =
+{
+	{
+		"5", "5", "5"
+	},
+	{
+		"4", "4", "4"
+	}
+};
+static dm_codes codes_5_5_X[2] =
+{
+	{
+		"5", "5", "X"
+	}
+};
+static dm_codes codes_66_66_66[2] =
+{
+	{
+		"66", "66", "66"
+	}
+};
+static dm_codes codes_6_6_6[2] =
+{
+	{
+		"6", "6", "6"
+	}
+};
+static dm_codes codes_7_7_7[2] =
+{
+	{
+		"7", "7", "7"
+	}
+};
+static dm_codes codes_8_8_8[2] =
+{
+	{
+		"8", "8", "8"
+	}
+};
+static dm_codes codes_94_94_94_or_4_4_4[2] =
+{
+	{
+		"94", "94", "94"
+	},
+	{
+		"4", "4", "4"
+	}
+};
+static dm_codes codes_9_9_9[2] =
+{
+	{
+		"9", "9", "9"
+	}
+};
+static dm_codes codes_X_X_6_or_X_X_X[2] =
+{
+	{
+		"X", "X", "6"
+	},
+	{
+		"X", "X", "X"
+	}
+};
+
+/* Coding for alternative following letters in sequence. */
+static dm_letter letter_A[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'U', NULL, codes_0_7_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CH[] =
+{
+	{
+		'S', NULL, codes_5_54_54
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CS[] =
+{
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_CZ[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_C[] =
+{
+	{
+		'H', letter_CH, codes_5_5_5_or_4_4_4
+	},
+	{
+		'K', NULL, codes_5_5_5_or_45_45_45
+	},
+	{
+		'S', letter_CS, codes_4_4_4
+	},
+	{
+		'Z', letter_CZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DR[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DS[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_DZ[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_D[] =
+{
+	{
+		'R', letter_DR, NULL
+	},
+	{
+		'S', letter_DS, codes_4_4_4
+	},
+	{
+		'T', NULL, codes_3_3_3
+	},
+	{
+		'Z', letter_DZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_E[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'U', NULL, codes_1_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_F[] =
+{
+	{
+		'B', NULL, codes_7_7_7
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_I[] =
+{
+	{
+		'A', NULL, codes_1_X_X
+	},
+	{
+		'E', NULL, codes_1_X_X
+	},
+	{
+		'O', NULL, codes_1_X_X
+	},
+	{
+		'U', NULL, codes_1_X_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_K[] =
+{
+	{
+		'H', NULL, codes_5_5_5
+	},
+	{
+		'S', NULL, codes_5_54_54
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_M[] =
+{
+	{
+		'N', NULL, codes_66_66_66
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_N[] =
+{
+	{
+		'M', NULL, codes_66_66_66
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_O[] =
+{
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_P[] =
+{
+	{
+		'F', NULL, codes_7_7_7
+	},
+	{
+		'H', NULL, codes_7_7_7
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_R[] =
+{
+	{
+		'S', NULL, codes_94_94_94_or_4_4_4
+	},
+	{
+		'Z', NULL, codes_94_94_94_or_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTSC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHTS[] =
+{
+	{
+		'C', letter_SCHTSC, NULL
+	},
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCHT[] =
+{
+	{
+		'C', letter_SCHTC, NULL
+	},
+	{
+		'S', letter_SCHTS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SCH[] =
+{
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', letter_SCHT, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SC[] =
+{
+	{
+		'H', letter_SCH, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHTC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHTS[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SHT[] =
+{
+	{
+		'C', letter_SHTC, NULL
+	},
+	{
+		'S', letter_SHTS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SH[] =
+{
+	{
+		'C', letter_SHC, NULL
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', letter_SHT, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STR[] =
+{
+	{
+		'S', NULL, codes_2_4_4
+	},
+	{
+		'Z', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STSC[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_STS[] =
+{
+	{
+		'C', letter_STSC, NULL
+	},
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ST[] =
+{
+	{
+		'C', letter_STC, NULL
+	},
+	{
+		'R', letter_STR, NULL
+	},
+	{
+		'S', letter_STS, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SZC[] =
+{
+	{
+		'S', NULL, codes_2_4_4
+	},
+	{
+		'Z', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_SZ[] =
+{
+	{
+		'C', letter_SZC, NULL
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'T', NULL, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_S[] =
+{
+	{
+		'C', letter_SC, codes_2_4_4
+	},
+	{
+		'D', NULL, codes_2_43_43
+	},
+	{
+		'H', letter_SH, codes_4_4_4
+	},
+	{
+		'T', letter_ST, codes_2_43_43
+	},
+	{
+		'Z', letter_SZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TR[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TS[] =
+{
+	{
+		'C', letter_TSC, NULL
+	},
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TTS[] =
+{
+	{
+		'C', letter_TTSC, NULL
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TT[] =
+{
+	{
+		'C', letter_TTC, NULL
+	},
+	{
+		'S', letter_TTS, codes_4_4_4
+	},
+	{
+		'Z', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_TZ[] =
+{
+	{
+		'S', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_T[] =
+{
+	{
+		'C', letter_TC, codes_4_4_4
+	},
+	{
+		'H', NULL, codes_3_3_3
+	},
+	{
+		'R', letter_TR, NULL
+	},
+	{
+		'S', letter_TS, codes_4_4_4
+	},
+	{
+		'T', letter_TT, NULL
+	},
+	{
+		'Z', letter_TZ, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_U[] =
+{
+	{
+		'E', NULL, codes_0_1_X
+	},
+	{
+		'I', NULL, codes_0_1_X
+	},
+	{
+		'J', NULL, codes_0_1_X
+	},
+	{
+		'Y', NULL, codes_0_1_X
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZDZ[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZD[] =
+{
+	{
+		'Z', letter_ZDZ, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZHDZ[] =
+{
+	{
+		'H', NULL, codes_2_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZHD[] =
+{
+	{
+		'Z', letter_ZHDZ, NULL
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZH[] =
+{
+	{
+		'D', letter_ZHD, codes_2_43_43
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZSC[] =
+{
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_ZS[] =
+{
+	{
+		'C', letter_ZSC, NULL
+	},
+	{
+		'H', NULL, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_Z[] =
+{
+	{
+		'D', letter_ZD, codes_2_43_43
+	},
+	{
+		'H', letter_ZH, codes_4_4_4
+	},
+	{
+		'S', letter_ZS, codes_4_4_4
+	},
+	{
+		'\0'
+	}
+};
+static dm_letter letter_[] =
+{
+	{
+		'A', letter_A, codes_0_X_X
+	},
+	{
+		'B', NULL, codes_7_7_7
+	},
+	{
+		'C', letter_C, codes_5_5_5_or_4_4_4
+	},
+	{
+		'D', letter_D, codes_3_3_3
+	},
+	{
+		'E', letter_E, codes_0_X_X
+	},
+	{
+		'F', letter_F, codes_7_7_7
+	},
+	{
+		'G', NULL, codes_5_5_5
+	},
+	{
+		'H', NULL, codes_5_5_X
+	},
+	{
+		'I', letter_I, codes_0_X_X
+	},
+	{
+		'J', NULL, codes_1_X_X_or_4_4_4
+	},
+	{
+		'K', letter_K, codes_5_5_5
+	},
+	{
+		'L', NULL, codes_8_8_8
+	},
+	{
+		'M', letter_M, codes_6_6_6
+	},
+	{
+		'N', letter_N, codes_6_6_6
+	},
+	{
+		'O', letter_O, codes_0_X_X
+	},
+	{
+		'P', letter_P, codes_7_7_7
+	},
+	{
+		'Q', NULL, codes_5_5_5
+	},
+	{
+		'R', letter_R, codes_9_9_9
+	},
+	{
+		'S', letter_S, codes_4_4_4
+	},
+	{
+		'T', letter_T, codes_3_3_3
+	},
+	{
+		'U', letter_U, codes_0_X_X
+	},
+	{
+		'V', NULL, codes_7_7_7
+	},
+	{
+		'W', NULL, codes_7_7_7
+	},
+	{
+		'X', NULL, codes_5_54_54
+	},
+	{
+		'Y', NULL, codes_1_X_X
+	},
+	{
+		'Z', letter_Z, codes_4_4_4
+	},
+	{
+		'a', NULL, codes_X_X_6_or_X_X_X
+	},
+	{
+		'e', NULL, codes_X_X_6_or_X_X_X
+	},
+	{
+		't', NULL, codes_3_3_3_or_4_4_4
+	},
+	{
+		'\0'
+	}
+};
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff_header.pl b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
new file mode 100755
index 0000000000..3e97e000ee
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
@@ -0,0 +1,288 @@
+#!/bin/perl
+#
+# Generation of types and lookup tables for Daitch-Mokotoff soundex.
+#
+# Copyright (c) 2021 Finance Norway
+# Author: Dag Lem <[email-masked]>
+#
+# Permission to use, copy, modify, and distribute this software and its
+# documentation for any purpose, without fee, and without a written agreement
+# is hereby granted, provided that the above copyright notice and this
+# paragraph and the following two paragraphs appear in all copies.
+#
+# IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+# DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+# LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+# DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+# AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+# ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+# PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+#
+
+use strict;
+use warnings;
+use utf8;
+use open IO => ':utf8', ':std';
+use Data::Dumper;
+
+# Parse code table and generate tree for letter transitions.
+my %codes;
+my %alternates;
+my $table = [{}, [["","",""]]];
+while (<DATA>) {
+	chomp;
+	my ($letters, $codes) = split(/\s+/);
+	my @codes = map { [ split(/,/) ] } split(/\|/, $codes);
+
+	# Find alternate code transitions for calculation of storage.
+	# The first character can never yield more than two alternate codes, and is not considered here.
+	if (@codes > 1) {
+		for my $j (1..2) {
+			for my $i (0..1) {
+				my ($a, $b) = (substr($codes[$i][$j], -1, 1), substr($codes[($i + 1)%2][$j], 0, 1));
+				$alternates{$a}{$b} = 1 if $a ne $b;
+			}
+		}
+	}
+	my $key = "codes_" . join("_or_", map { join("_", @$_) } @codes);
+	my $val = join(",\n", map { "\t{\n\t\t" . join(", ", map { "\"$_\"" } @$_) . "\n\t}" } @codes);
+	$codes{$key} = $val;
+
+	for my $letter (split(/,/, $letters)) {
+		my $ref = $table->[0];
+		# Link each character to the next in the letter combination.
+		my @c = split(//, $letter);
+		my $last_c = pop(@c);
+		for my $c (@c) {
+			$ref->{$c} //= [ {}, undef ];
+			$ref->{$c}[0] //= {};
+			$ref = $ref->{$c}[0];
+		}
+		# The sound code for the letter combination is stored at the last character.
+		$ref->{$last_c}[1] = $key;
+	}
+}
+close(DATA);
+
+# Find the maximum number of alternate codes in one position.
+my $alt_x = $alternates{"X"};
+while (my ($k, $v) = each %alternates) {
+	if (defined delete $v->{"X"}) {
+		for my $x (keys %$alt_x) {
+			$v->{$x} = 1;
+		}
+	}
+}
+my $max_alt = (reverse sort (2, map { scalar keys %$_ } values %alternates))[0];
+
+# The maximum number of nodes and leaves in the soundex tree.
+# These are safe estimates, but in practice somewhat higher than the actual maximums.
+# Note that the first character can never yield more than two alternate codes,
+# hence the calculations are performed as sums of two subtrees.
+my $digits = 6;
+# Number of nodes (sum of geometric progression).
+my $max_nodes = 2 + 2*(1 - $max_alt**($digits - 1))/(1 - $max_alt);
+# Number of leaves (exponential of base number).
+my $max_leaves = 2*$max_alt**($digits - 2);
+
+print <<EOF;
+/*
+ * Types and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <dag\@nimrod.no>
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include <stdlib.h>
+
+#define DM_MAX_CODE_DIGITS $digits
+#define DM_MAX_ALTERNATE_CODES $max_alt
+#define DM_MAX_NODES $max_nodes
+#define DM_MAX_LEAVES $max_leaves
+#define DM_MAX_SOUNDEX_CHARS (DM_MAX_NODES*(DM_MAX_CODE_DIGITS + 1))
+
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[3];	/* Start of name, before a vowel, any other */
+
+/* Letter in input sequence */
+struct dm_letter
+{
+	char		letter;			/* Present letter in sequence */
+	struct dm_letter *letters;	/* List of possible successive letters */
+	dm_codes   *codes;			/* Code sequence(s) for complete sequence */
+};
+
+/* Node in soundex code tree */
+struct dm_node
+{
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_MAX_CODE_DIGITS + 1];	/* Soundex code */
+	int			is_leaf;		/* Candidate for complete soundex code */
+	int			last_update;	/* Letter number for last update of node */
+	char		code_digit;		/* Last code digit, 0 - 9 */
+
+	/*
+	 * One or two alternate code digits leading to this node. If there are two
+	 * digits, one of them is always an 'X'. Repeated code digits and 'X' lead
+	 * back to the same node.
+	 */
+	char		prev_code_digits[2];
+	/* One or two alternate code digits moving forward. */
+	char		next_code_digits[2];
+	/* ORed together code index(es) used to reach current node. */
+	int			prev_code_index;
+	int			next_code_index;
+	/* Nodes branching out from this node. */
+	struct dm_node *next_nodes[DM_MAX_ALTERNATE_CODES + 1];
+};
+
+typedef struct dm_letter dm_letter;
+typedef struct dm_node dm_node;
+
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+EOF
+
+for my $key (sort keys %codes) {
+	print "static dm_codes $key\[2\] =\n{\n" . $codes{$key} . "\n};\n";
+}
+
+print <<EOF;
+
+/* Coding for alternative following letters in sequence. */
+EOF
+
+sub hash2code {
+	my ($ref, $letter) = @_;
+
+	my @letters = ();
+
+	my $h = $ref->[0];
+	for my $key (sort keys %$h) {
+		$ref = $h->{$key};
+		my $children = "NULL";
+		if (defined $ref->[0]) {
+			$children = "letter_$letter$key";
+			hash2code($ref, "$letter$key");
+		}
+		my $codes = $ref->[1] // "NULL";
+		push(@letters, "\t{\n\t\t'$key', $children, $codes\n\t}");
+	}
+
+	print "static dm_letter letter_$letter\[\] =\n{\n";
+	for (@letters) {
+		print "$_,\n";
+	}
+	print "\t{\n\t\t'\\0'\n\t}\n";
+	print "};\n";
+}
+
+hash2code($table, '');
+
+
+# Table adapted from https://www.jewishgen.org/InfoFiles/Soundex.html
+#
+# X = NC (not coded)
+#
+# Note that the following letters are coded with substitute letters
+#
+# Ą => a (use '[' for table lookup)
+# Ę => e (use '\\' for table lookup)
+# Ţ => t (use ']' for table lookup)
+#
+# The rule for "UE" below does not correspond to the table referred to above,
+# however it is used by all other known implementations, including the one at
+# https://www.jewishgen.org/jos/jossound.htm (try e.g. "bouey").
+
+__DATA__
+AI,AJ,AY				0,1,X
+AU						0,7,X
+a						X,X,6|X,X,X
+A						0,X,X
+B						7,7,7
+CHS						5,54,54
+CH						5,5,5|4,4,4
+CK						5,5,5|45,45,45
+CZ,CS,CSZ,CZS			4,4,4
+C						5,5,5|4,4,4
+DRZ,DRS					4,4,4
+DS,DSH,DSZ				4,4,4
+DZ,DZH,DZS				4,4,4
+D,DT					3,3,3
+EI,EJ,EY				0,1,X
+EU						1,1,X
+e						X,X,6|X,X,X
+E						0,X,X
+FB						7,7,7
+F						7,7,7
+G						5,5,5
+H						5,5,X
+IA,IE,IO,IU				1,X,X
+I						0,X,X
+J						1,X,X|4,4,4
+KS						5,54,54
+KH						5,5,5
+K						5,5,5
+L						8,8,8
+MN						66,66,66
+M						6,6,6
+NM						66,66,66
+N						6,6,6
+OI,OJ,OY				0,1,X
+O						0,X,X
+P,PF,PH					7,7,7
+Q						5,5,5
+RZ,RS					94,94,94|4,4,4
+R						9,9,9
+SCHTSCH,SCHTSH,SCHTCH	2,4,4
+SCH						4,4,4
+SHTCH,SHCH,SHTSH		2,4,4
+SHT,SCHT,SCHD			2,43,43
+SH						4,4,4
+STCH,STSCH,SC			2,4,4
+STRZ,STRS,STSH			2,4,4
+ST						2,43,43
+SZCZ,SZCS				2,4,4
+SZT,SHD,SZD,SD			2,43,43
+SZ						4,4,4
+S						4,4,4
+TCH,TTCH,TTSCH			4,4,4
+TH						3,3,3
+TRZ,TRS					4,4,4
+TSCH,TSH				4,4,4
+TS,TTS,TTSZ,TC			4,4,4
+TZ,TTZ,TZS,TSZ			4,4,4
+t						3,3,3|4,4,4
+T						3,3,3
+UI,UJ,UY,UE				0,1,X
+U						0,X,X
+V						7,7,7
+W						7,7,7
+X						5,54,54
+Y						1,X,X
+ZDZ,ZDZH,ZHDZH			2,4,4
+ZD,ZHD					2,43,43
+ZH,ZS,ZSCH,ZSH			4,4,4
+Z						4,4,4
diff --git a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
index 493c95cdfa..d778facd49 100644
--- a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
+++ b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
@@ -65,3 +65,224 @@ SELECT dmetaphone_alt('gumbo');
  KMP
 (1 row)
 
+-- Wovels
+-- "Difficult" cases, likely to cause trouble for other implementations.
+SELECT daitch_mokotoff('BESST');
+SELECT daitch_mokotoff('BOUEY');
+ 710000
+SELECT daitch_mokotoff('HANNMANN');
+ 566600
+SELECT daitch_mokotoff('MCCOYJR');
+ 651900 654900 654190 654490 645190 645490 641900 644900
+SELECT daitch_mokotoff('ACCURSO');
+ 059400 054000 054940 054400 045940 045400 049400 044000
+SELECT daitch_mokotoff('BIERSCHBACH');
+ 794575 794574 794750 794740 745750 745740 747500 747400
index f05dc28ffb..c83572fe76 100644
@@ -19,3 +19,60 @@ SELECT metaphone('GUMBO', 4);
 
+-- "Difficult" cases, likely to cause trouble for other implementations.
+SELECT daitch_mokotoff('BESST');
+SELECT daitch_mokotoff('BOUEY');
+SELECT daitch_mokotoff('HANNMANN');
+SELECT daitch_mokotoff('MCCOYJR');
+SELECT daitch_mokotoff('ACCURSO');
+SELECT daitch_mokotoff('BIERSCHBACH');
index 382e54be91..08781778f8 100644
@@ -241,4 +241,101 @@ test=# SELECT dmetaphone('gumbo');
 </screen>
  </sect2>
 
+ <sect2>
+-- (no recalculation on table row recheck).
+INSERT INTO s VALUES ('John Doe');
+INSERT INTO s VALUES ('Jane Roe');
+INSERT INTO s VALUES ('Public John Q.');
+INSERT INTO s VALUES ('George Best');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('jane doe');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('john public');
+SELECT * FROM s WHERE soundex_tsvector(nm) @@ soundex_tsquery('besst, giorgio');
+</programlisting>
+ </sect2>
+
 </sect1>

---

From: Ian Lawrence Barwick <[email-masked]>
Date: Wed, 30 Nov 2022 21:56:29 +0900

Hi Dag

2022年2月3日(木) 23:27 Dag Lem <[email-masked]>:
>
> Hi,
>
> Just some minor adjustments to the patch:
>
> * Removed call to locale-dependent toupper()
> * Cleaned up input normalization

This patch was marked as "Waiting on Author" in the CommitFest entry [1]
but I see you provided an updated version which hasn't received any feedback,
so I've move this to the next CommitFest [2] and set it to "Needs Review".

[1] https://commitfest.postgresql.org/40/3451/
[2] https://commitfest.postgresql.org/41/3451/

> I have been asked to sign up to review a commitfest patch or patches -
> unfortunately I've been ill with COVID-19 and it's not until now that
> I feel well enough to have a look.
>
> Julien: I'll have a look at https://commitfest.postgresql.org/36/3468/
> as you suggested (https://commitfest.postgresql.org/36/3379/ seems to
> have been reviewed now).
>
> If there are other suggestions for a patch or patches to review for
> someone new to PostgreSQL internals, I'd be grateful for that.

I see you provided some feedback on https://commitfest.postgresql.org/36/3468/,
though the patch seems to have not been accepted (but not conclusively rejected
either). If you still have the chance to review another patch (or more) it would
be much appreciated, as there's quite a few piling up. Things like documentation
or small improvements to client applications are always a good place to start.
Reviews can be provided at any time, there's no need to wait for the next
CommitFest.

Regards

Ian Barwick

---

From: Dag Lem <[email-masked]>
Date: Mon, 05 Dec 2022 14:24:49 +0100

Hi Ian,

> Reviews can be provided at any time, there's no need to wait for the next

OK, I'll try to find another patch to review.

Regards

Dag Lem

---

From: Andres Freund <[email-masked]>
Date: Wed, 7 Dec 2022 10:56:56 -0800

Hi,

> * Cleaned up input normalization

This patch currently fails in cfbot, likely because meson.build needs to be
adjusted (this didn't exist at the time you submitted this version of the
patch):

[23:43:34.796] contrib/fuzzystrmatch/meson.build:18:0: ERROR: File fuzzystrmatch--1.1.sql does not exist.

>  PGFILEDESC = "fuzzystrmatch - similarities and distance between strings"

The patch seems to remove fuzzystrmatch--1.1.sql - I suggest not doing
that. In recent years our approach has been to just keep the "base version" of
the upgrade script, with extension creation running through the upgrade
scripts.

> +#include "daitch_mokotoff.h"

Postgres policy is that the include of "postgres.h" has to be the first
include in every .c file.

> +	tmp_soundex = palloc(DM_MAX_SOUNDEX_CHARS);

Seems that just using StringInfo to hold the soundex output would work better
than a static allocation?

> +	if (!_daitch_mokotoff(string, tmp_soundex, DM_MAX_SOUNDEX_CHARS))

We imo shouldn't introduce new functions starting with _.

> +									 dm_node * node, char code_digit)

PG code style is to have a line break between a function defintion's return
type and the function name - like you actually do above.

> +/* Mapping from ISO8859-1 to upper-case ASCII */
> +static const char tr_iso8859_1_to_ascii_upper[] =
> +/*
> +"`abcdefghijklmnopqrstuvwxyz{|}~                                  ¡¢£¤¥¦§¨©ª«¬ ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
> +*/
> +"`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~                                  !                             ?AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDSAAAAAAECEEEEIIIIDNOOOOO/OUUUUYDY";
> +
> +static char
> +iso8859_1_to_ascii_upper(unsigned char c)
> +{
> +	return c >= 0x60 ? tr_iso8859_1_to_ascii_upper[c - 0x60] : c;
> +}
> +
> +

It seems decidedly not great to have custom encoding conversion routines in a
contrib module. Is there any way we can avoid this?

> +	/* First letter. */
> +	if (!(codes = read_letter(word, &i)))
> +	{

So this allocates the worst case memory usage, is that right? That's quite a
bit of memory. Shouldn't nodes be allocated dynamically?

Instead of carefully freeing individual memory allocations, I think it be
better to create a temporary memory context, allocate the necessary nodes etc
on demand, and destroy the temporary memory context at the end.

> +static dm_codes codes_0_1_X[2] =

Any reason these aren't all const?

It's not clear to me where the intended line between the .h and .c file is.

> + * Types and lookup tables for Daitch-Mokotoff Soundex

If we generate the code, why is the generated header included in the commit?

> +typedef struct dm_node dm_node;

Why is all this in the generated header? It needs DM_MAX_ALTERNATE_CODES etc,
but it seems that the structs could just be defined in the .c file.

> +# Table adapted from https://www.jewishgen.org/InfoFiles/Soundex.html

What does "adapted" mean here? And what's the path to updating the data?

Greetings,

Andres Freund

---

From: Dag Lem <[email-masked]>
Date: Wed, 21 Dec 2022 10:26:05 +0100

Hi Andreas,

Thank you for your detailed and constructive review!

I have made a conscientuous effort to address all the issues you point
out, please see comments below.

[...]

> the upgrade script, with extension creation running through the upgrade

OK, I have now kept fuzzystrmatch--1.1.sql, and omitted
fuzzystrmatch--1.2.sql

Both the Makefile and meson.build are updated to handle the new files,
including the generated header.

> include in every .c file.

OK, fixed.

> than a static allocation?

OK, fixed.

> We imo shouldn't introduce new functions starting with _.

OK, fixed. Note that I just followed the existing pattern in
fuzzystrmatch.c there.

[...]

> type and the function name - like you actually do above.

OK, fixed. Both pgindent and I must have missed that particular
function.

>> +"`abcdefghijklmnopqrstuvwxyz{|}~ ¡¢£¤¥¦§¨©ª«¬
>> ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
>> +*/
>> +"`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~ !
>> ?AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDSAAAAAAECEEEEIIIIDNOOOOO/OUUUUYDY";
>> +
>> +static char

I have now replaced the custom UTF-8 decode with calls to
utf8_to_unicode and pg_utf_mblen, and simplified the subsequent
conversion to ASCII. Hopefully this makes the conversion code more
palatable.

I don't see how the conversion to ASCII could be substantially
simplified further. The conversion maps lowercase and 8 bit ISO8859-1
characters to ASCII via uppercasing, removal of accents, and discarding
of special characters. In addition to that, it maps (the non-ISO8859-1)
Ą, Ę, and Ţ/Ț from the coding chart to [, \, and ]. After this, a simple
O(1) table lookup can be used to retrieve the soundex code tree for a
letter sequence.

> on demand, and destroy the temporary memory context at the end.

Yes, the one-time allocation was intended to cover the worst case memory
usage. This was done to avoid any performance hit incurred by allocating
and deallocating memory for each new node in the soundex code tree.

I have rewritten the bookeeping of nodes in the soundex code tree to use
linked lists, and have followed your advice to use a temporary memory
context for allocation.

I also made an optimization by excluding completed soundex nodes from
the next letter iteration. This seems to offset any allocation overhead
- the performance is more or less the same as before.

> Any reason these aren't all const?

No reason why they can't be :-) They are now changed to const.

> If we generate the code, why is the generated header included in the commit?

This was mainly to have the content available for reference without
having to generate the header. I have removed the file - after the
change you suggest below, the struct declarations are available in the
.c file anyway.

>> + * digits, one of them is always an 'X'. Repeated code digits and
>> X' lead

To accomplish this, I had to rearrange the code a bit. The structs are
now all declared in daitch_mokotoff.c, and the generated header is
included inbetween them.

> What does "adapted" mean here? And what's the path to updating the data?

It means that the original soundex coding chart, which is referred to,
has been converted to a machine readable format, with a few
modifications. These modifications are outlined further down in the
comments. I expanded a bit on the comments, hopefully making things
clearer.

I don't think there is much to be said about updating the data - that's
simply a question of modifying the table and regenerating the header
file. It goes without saying that making changes requires an
understanding of the soundex coding, which is explained in the
reference. However if anything should be unclear, please do point out
what should be explained better.

> Andres Freund

Thanks again, and a Merry Christmas to you and all the other PostgreSQL
hackers!

Best regards,

Dag Lem

index 0704894f88..12baf2d884 100644
@@ -3,14 +3,15 @@
 
 EXTENSION = fuzzystrmatch
-DATA = fuzzystrmatch--1.1.sql fuzzystrmatch--1.0--1.1.sql
+DATA = fuzzystrmatch--1.1.sql fuzzystrmatch--1.1--1.2.sql fuzzystrmatch--1.0--1.1.sql
 PGFILEDESC = "fuzzystrmatch - similarities and distance between strings"
 
-REGRESS = fuzzystrmatch
+REGRESS = fuzzystrmatch fuzzystrmatch_utf8
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
@@ -22,3 +23,14 @@ top_builddir = ../..
 include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
+
+# Force this dependency to be known even without dependency info built:
+daitch_mokotoff.o: daitch_mokotoff.h
+
+daitch_mokotoff.h: daitch_mokotoff_header.pl
+	perl $< $@
+
+distprep: daitch_mokotoff.h
+
+maintainer-clean:
+	rm -f daitch_mokotoff.h
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff.c b/contrib/fuzzystrmatch/daitch_mokotoff.c
new file mode 100644
index 0000000000..d4ad95c283
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff.c
@@ -0,0 +1,596 @@
+/*
+ * Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <[email-masked]>
+ *
+ * This implementation of the Daitch-Mokotoff Soundex System aims at high
+ * performance.
+ *
+ * - The processing of each phoneme is initiated by an O(1) table lookup.
+ * - For phonemes containing more than one character, a coding tree is traversed
+ *   to process the complete phoneme.
+ * - The (alternate) soundex codes are produced digit by digit in-place in
+ *   another tree structure.
+ *
+ *  References:
+ *
+ * https://www.avotaynu.com/soundex.htm
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * https://familypedia.fandom.com/wiki/Daitch-Mokotoff_Soundex
+ * https://stevemorse.org/census/soundex.html (dmlat.php, dmsoundex.php)
+ * https://github.com/apache/commons-codec/ (dmrules.txt, DaitchMokotoffSoundex.java)
+ * https://metacpan.org/pod/Text::Phonetic (DaitchMokotoff.pm)
+ *
+ * A few notes on other implementations:
+ *
+ * - All other known implementations have the same unofficial rules for "UE",
+ *   these are also adapted by this implementation (0, 1, NC).
+ * - The only other known implementation which is capable of generating all
+ *   correct soundex codes in all cases is the JOS Soundex Calculator at
+ *   https://www.jewishgen.org/jos/jossound.htm
+ * - "J" is considered (only) a vowel in dmlat.php
+ * - The official rules for "RS" are commented out in dmlat.php
+ * - Identical code digits for adjacent letters are not collapsed correctly in
+ *   dmsoundex.php when double digit codes are involved. E.g. "BESST" yields
+ *   744300 instead of 743000 as for "BEST".
+ * - "J" is considered (only) a consonant in DaitchMokotoffSoundex.java
+ * - "Y" is not considered a vowel in DaitchMokotoffSoundex.java
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+*/
+
+#include "postgres.h"
+
+#include "lib/stringinfo.h"
+#include "mb/pg_wchar.h"
+#include "utils/builtins.h"
+#include "utils/memutils.h"
+
+
+/*
+ * The soundex coding chart table is adapted from from
+ * https://www.jewishgen.org/InfoFiles/Soundex.html
+ * See daitch_mokotoff_header.pl for details.
+*/
+
+#define DM_CODE_DIGITS 6
+
+/* Coding chart table: Soundex codes */
+typedef char dm_code[2 + 1];	/* One or two sequential code digits + NUL */
+typedef dm_code dm_codes[3];	/* Start of name, before a vowel, any other */
+
+/* Coding chart table: Letter in input sequence */
+struct dm_letter
+{
+	char		letter;			/* Present letter in sequence */
+	const struct dm_letter *letters;	/* List of possible successive letters */
+	const		dm_codes *codes;	/* Code sequence(s) for complete sequence */
+};
+
+typedef struct dm_letter dm_letter;
+
+/* Generated coding chart table */
+#include "daitch_mokotoff.h"
+
+/* Node in soundex code tree */
+struct dm_node
+{
+	int			soundex_length; /* Length of generated soundex code */
+	char		soundex[DM_CODE_DIGITS + 1];	/* Soundex code */
+	int			is_leaf;		/* Candidate for complete soundex code */
+	int			last_update;	/* Letter number for last update of node */
+	char		code_digit;		/* Last code digit, 0 - 9 */
+
+	/*
+	 * One or two alternate code digits leading to this node. If there are two
+	 * digits, one of them is always an 'X'. Repeated code digits and 'X' lead
+	 * back to the same node.
+	 */
+	char		prev_code_digits[2];
+	/* One or two alternate code digits moving forward. */
+	char		next_code_digits[2];
+	/* ORed together code index(es) used to reach current node. */
+	int			prev_code_index;
+	int			next_code_index;
+	/* Nodes branching out from this node. */
+	struct dm_node *children[DM_MAX_ALTERNATE_CODES + 1];
+	/* Next node in linked list. Alternating index for each iteration. */
+	struct dm_node *next[2];
+};
+
+typedef struct dm_node dm_node;
+
+
+/* Internal C implementation */
+static int	daitch_mokotoff_coding(char *word, StringInfo soundex);
+
+
+PG_FUNCTION_INFO_V1(daitch_mokotoff);
+
+Datum
+daitch_mokotoff(PG_FUNCTION_ARGS)
+{
+	text	   *arg = PG_GETARG_TEXT_PP(0);
+	char	   *string;
+	StringInfoData soundex;
+	text	   *retval;
+	MemoryContext old_ctx,
+				tmp_ctx;
+
+	tmp_ctx = AllocSetContextCreate(CurrentMemoryContext,
+									"daitch_mokotoff temporary context",
+									ALLOCSET_DEFAULT_SIZES);
+	old_ctx = MemoryContextSwitchTo(tmp_ctx);
+
+	string = pg_server_to_any(text_to_cstring(arg), VARSIZE_ANY_EXHDR(arg), PG_UTF8);
+	initStringInfo(&soundex);
+
+	if (!daitch_mokotoff_coding(string, &soundex))
+	{
+		/* No encodable characters in input. */
+		MemoryContextSwitchTo(old_ctx);
+		MemoryContextDelete(tmp_ctx);
+		PG_RETURN_NULL();
+	}
+
+	string = pg_any_to_server(soundex.data, soundex.len, PG_UTF8);
+	MemoryContextSwitchTo(old_ctx);
+	retval = cstring_to_text(string);
+	MemoryContextDelete(tmp_ctx);
+
+	PG_RETURN_TEXT_P(retval);
+}
+
+
+/* Template for new node in soundex code tree. */
+static const dm_node start_node = {
+	.soundex_length = 0,
+	.soundex = "000000 ",		/* Six digits + joining space */
+	.is_leaf = 0,
+	.last_update = 0,
+	.code_digit = '\0',
+	.prev_code_digits = {'\0', '\0'},
+	.next_code_digits = {'\0', '\0'},
+	.prev_code_index = 0,
+	.next_code_index = 0,
+	.children = {NULL},
+	.next = {NULL}
+};
+
+/* Dummy soundex codes at end of input. */
+static const dm_codes end_codes[2] =
+{
+	{
+		"X", "X", "X"
+	}
+};
+
+
+/* Initialize soundex code tree node for next code digit. */
+static void
+initialize_node(dm_node * node, int last_update)
+{
+	if (node->last_update < last_update)
+	{
+		node->prev_code_digits[0] = node->next_code_digits[0];
+		node->prev_code_digits[1] = node->next_code_digits[1];
+		node->next_code_digits[0] = '\0';
+		node->next_code_digits[1] = '\0';
+		node->prev_code_index = node->next_code_index;
+		node->next_code_index = 0;
+		node->is_leaf = 0;
+		node->last_update = last_update;
+	}
+}
+
+
+/* Update soundex code tree node with next code digit. */
+static void
+add_next_code_digit(dm_node * node, int code_index, char code_digit)
+{
+	/* OR in index 1 or 2. */
+	node->next_code_index |= code_index;
+
+	if (!node->next_code_digits[0])
+	{
+		node->next_code_digits[0] = code_digit;
+	}
+	else if (node->next_code_digits[0] != code_digit)
+	{
+		node->next_code_digits[1] = code_digit;
+	}
+}
+
+
+/* Mark soundex code tree node as leaf. */
+static void
+set_leaf(dm_node * first_node[2], dm_node * last_node[2], dm_node * node, int ix_node)
+{
+	if (!node->is_leaf)
+	{
+		node->is_leaf = 1;
+
+		if (first_node[ix_node] == NULL)
+		{
+			first_node[ix_node] = node;
+		}
+		else
+		{
+			last_node[ix_node]->next[ix_node] = node;
+		}
+
+		last_node[ix_node] = node;
+		node->next[ix_node] = NULL;
+	}
+}
+
+
+/* Find next node corresponding to code digit, or create a new node. */
+static dm_node *
+find_or_create_child_node(dm_node * parent, char code_digit, StringInfo soundex)
+{
+	dm_node   **nodes;
+	dm_node    *node;
+	int			i;
+
+	for (nodes = parent->children, i = 0; (node = nodes[i]); i++)
+	{
+		if (node->code_digit == code_digit)
+		{
+			/* Found existing child node. Skip completed nodes. */
+			return node->soundex_length < DM_CODE_DIGITS ? node : NULL;
+		}
+	}
+
+	/* Create new child node. */
+	Assert(i < DM_MAX_ALTERNATE_CODES);
+	node = palloc(sizeof(dm_node));
+	nodes[i] = node;
+
+	*node = start_node;
+	memcpy(node->soundex, parent->soundex, sizeof(parent->soundex));
+	node->soundex_length = parent->soundex_length;
+	node->soundex[node->soundex_length++] = code_digit;
+	node->code_digit = code_digit;
+	node->next_code_index = node->prev_code_index;
+
+	if (node->soundex_length < DM_CODE_DIGITS)
+	{
+		return node;
+	}
+	else
+	{
+		/* Append completed soundex code to soundex string. */
+		appendBinaryStringInfoNT(soundex, node->soundex, DM_CODE_DIGITS + 1);
+		return NULL;
+	}
+}
+
+
+/* Update node for next code digit(s). */
+static void
+update_node(dm_node * first_node[2], dm_node * last_node[2], dm_node * node, int ix_node,
+			int letter_no, int prev_code_index, int next_code_index,
+			const char *next_code_digits, int digit_no,
+			StringInfo soundex)
+{
+	int			i;
+	char		next_code_digit = next_code_digits[digit_no];
+	int			num_dirty_nodes = 0;
+	dm_node    *dirty_nodes[2];
+
+	initialize_node(node, letter_no);
+
+	if (node->prev_code_index && !(node->prev_code_index & prev_code_index))
+	{
+		/*
+		 * If the sound (vowel / consonant) of this letter encoding doesn't
+		 * correspond to the coding index of the previous letter, we skip this
+		 * letter encoding. Note that currently, only "J" can be either a
+		 * vowel or a consonant.
+		 */
+		return;
+	}
+
+	if (next_code_digit == 'X' ||
+		(digit_no == 0 &&
+		 (node->prev_code_digits[0] == next_code_digit ||
+		  node->prev_code_digits[1] == next_code_digit)))
+	{
+		/* The code digit is the same as one of the previous (i.e. not added). */
+		dirty_nodes[num_dirty_nodes++] = node;
+	}
+
+	if (next_code_digit != 'X' &&
+		(digit_no > 0 ||
+		 node->prev_code_digits[0] != next_code_digit ||
+		 node->prev_code_digits[1]))
+	{
+		/* The code digit is different from one of the previous (i.e. added). */
+		node = find_or_create_child_node(node, next_code_digit, soundex);
+		if (node)
+		{
+			initialize_node(node, letter_no);
+			dirty_nodes[num_dirty_nodes++] = node;
+		}
+	}
+
+	for (i = 0; i < num_dirty_nodes; i++)
+	{
+		/* Add code digit leading to the current node. */
+		add_next_code_digit(dirty_nodes[i], next_code_index, next_code_digit);
+
+		if (next_code_digits[++digit_no])
+		{
+			update_node(first_node, last_node, dirty_nodes[i], ix_node,
+						letter_no, prev_code_index, next_code_index,
+						next_code_digits, digit_no,
+						soundex);
+		}
+		else
+		{
+			/* Add incomplete leaf node to linked list. */
+			set_leaf(first_node, last_node, dirty_nodes[i], ix_node);
+		}
+	}
+}
+
+
+/* Update soundex tree leaf nodes. */
+static void
+update_leaves(dm_node * first_node[2], int *ix_node, int letter_no,
+			  const dm_codes * codes, const dm_codes * next_codes,
+			  StringInfo soundex)
+{
+	int			i,
+				j,
+				code_index;
+	dm_node    *node,
+			   *last_node[2];
+	const		dm_code *code,
+			   *next_code;
+	int			ix_node_next = (*ix_node + 1) & 1;	/* Alternating index: 0, 1 */
+
+	/* Initialize for new linked list of leaves. */
+	first_node[ix_node_next] = NULL;
+	last_node[ix_node_next] = NULL;
+
+	/* Process all nodes. */
+	for (node = first_node[*ix_node]; node; node = node->next[*ix_node])
+	{
+		/* One or two alternate code sequences. */
+		for (i = 0; i < 2 && (code = codes[i]) && code[0][0]; i++)
+		{
+			/* Coding for previous letter - before vowel: 1, all other: 2 */
+			int			prev_code_index = (code[0][0] > '1') + 1;
+
+			/* One or two alternate next code sequences. */
+			for (j = 0; j < 2 && (next_code = next_codes[j]) && next_code[0][0]; j++)
+			{
+				/* Determine which code to use. */
+				if (letter_no == 0)
+				{
+					/* This is the first letter. */
+					code_index = 0;
+				}
+				else if (next_code[0][0] <= '1')
+				{
+					/* The next letter is a vowel. */
+					code_index = 1;
+				}
+				else
+				{
+					/* All other cases. */
+					code_index = 2;
+				}
+
+				/* One or two sequential code digits. */
+				update_node(first_node, last_node, node, ix_node_next,
+							letter_no, prev_code_index, code_index,
+							code[code_index], 0,
+							soundex);
+			}
+		}
+	}
+
+	*ix_node = ix_node_next;
+}
+
+
+/* Mapping from ISO8859-1 to upper-case ASCII */
+static const char iso8859_1_to_ascii_upper[] =
+/*
+"`abcdefghijklmnopqrstuvwxyz{|}~                                  ¡¢£¤¥¦§¨©ª«¬ ®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüýþÿ"
+*/
+"`ABCDEFGHIJKLMNOPQRSTUVWXYZ{|}~                                  !                             ?AAAAAAECEEEEIIIIDNOOOOO*OUUUUYDSAAAAAAECEEEEIIIIDNOOOOO/OUUUUYDY";
+
+
+/* Return next character, converted from UTF-8 to uppercase ASCII. */
+static char
+read_char(unsigned char *str, int *ix)
+{
+	/* Substitute character for skipped code points. */
+	const char	na = '\x1a';
+	pg_wchar	c;
+
+	/* Decode UTF-8 character to ISO 10646 code point. */
+	str += *ix;
+	c = utf8_to_unicode(str);
+	*ix += pg_utf_mblen(str);
+
+	if (c >= (unsigned char) '[' && c <= (unsigned char) ']')
+	{
+		/* ASCII characters [, \, and ] are reserved for Ą, Ę, and Ţ/Ț. */
+		return na;
+	}
+	else if (c < 0x60)
+	{
+		/* Non-lowercase ASCII character. */
+		return c;
+	}
+	else if (c < 0x100)
+	{
+		/* ISO-8859-1 code point, converted to upper-case ASCII. */
+		return iso8859_1_to_ascii_upper[c - 0x60];
+	}
+	else
+	{
+		/* Conversion of non-ASCII characters in the coding chart. */
+		switch (c)
+		{
+			case 0x0104:
+			case 0x0105:
+				/* Ą/ą */
+				return '[';
+			case 0x0118:
+			case 0x0119:
+				/* Ę/ę */
+				return '\\';
+			case 0x0162:
+			case 0x0163:
+			case 0x021A:
+			case 0x021B:
+				/* Ţ/ţ or Ț/ț */
+				return ']';
+			default:
+				return na;
+		}
+	}
+}
+
+
+/* Read next ASCII character, skipping any characters not in [A-\]]. */
+static char
+read_valid_char(char *str, int *ix)
+{
+	char		c;
+
+	while ((c = read_char((unsigned char *) str, ix)))
+	{
+		if (c >= 'A' && c <= ']')
+		{
+			break;
+		}
+	}
+
+	return c;
+}
+
+
+/* Return sound coding for "letter" (letter sequence) */
+static const dm_codes *
+read_letter(char *str, int *ix)
+{
+	char		c,
+				cmp;
+	int			i,
+				j;
+	const		dm_letter *letters;
+	const		dm_codes *codes;
+
+	/* First letter in sequence. */
+	if (!(c = read_valid_char(str, ix)))
+	{
+		return NULL;
+	}
+	letters = &letter_[c - 'A'];
+	codes = letters->codes;
+	i = *ix;
+
+	/* Any subsequent letters in sequence. */
+	while ((letters = letters->letters) && (c = read_valid_char(str, &i)))
+	{
+		for (j = 0; (cmp = letters[j].letter); j++)
+		{
+			if (cmp == c)
+			{
+				/* Letter found. */
+				letters = &letters[j];
+				if (letters->codes)
+				{
+					/* Coding for letter sequence found. */
+					codes = letters->codes;
+					*ix = i;
+				}
+				break;
+			}
+		}
+		if (!cmp)
+		{
+			/* The sequence of letters has no coding. */
+			break;
+		}
+	}
+
+	return codes;
+}
+
+
+/* Generate all Daitch-Mokotoff soundex codes for word, separated by space. */
+static int
+daitch_mokotoff_coding(char *word, StringInfo soundex)
+{
+	int			i = 0;
+	int			letter_no = 0;
+	int			ix_node = 0;
+	const		dm_codes *codes,
+			   *next_codes;
+	dm_node    *first_node[2],
+			   *node;
+
+	/* First letter. */
+	if (!(codes = read_letter(word, &i)))
+	{
+		/* No encodable character in input. */
+		return 0;
+	}
+
+	/* Starting point. */
+	first_node[ix_node] = palloc(sizeof(dm_node));
+	*first_node[ix_node] = start_node;
+
+	/*
+	 * Loop until either the word input is exhausted, or all generated soundex
+	 * codes are completed to six digits.
+	 */
+	while (codes && first_node[ix_node])
+	{
+		next_codes = read_letter(word, &i);
+
+		/* Update leaf nodes. */
+		update_leaves(first_node, &ix_node, letter_no,
+					  codes, next_codes ? next_codes : end_codes,
+					  soundex);
+
+		codes = next_codes;
+		letter_no++;
+	}
+
+	/* Append all remaining (incomplete) soundex codes. */
+	for (node = first_node[ix_node]; node; node = node->next[ix_node])
+	{
+		appendBinaryStringInfoNT(soundex, node->soundex, DM_CODE_DIGITS + 1);
+	}
+
+	/* Terminate string at the final space. */
+	soundex->len--;
+	soundex->data[soundex->len] = '\0';
+
+	return 1;
+}
diff --git a/contrib/fuzzystrmatch/daitch_mokotoff_header.pl b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
new file mode 100755
index 0000000000..807b5fb8c5
--- /dev/null
+++ b/contrib/fuzzystrmatch/daitch_mokotoff_header.pl
@@ -0,0 +1,260 @@
+#!/bin/perl
+#
+# Generation of types and lookup tables for Daitch-Mokotoff soundex.
+#
+# Copyright (c) 2021 Finance Norway
+# Author: Dag Lem <[email-masked]>
+#
+# Permission to use, copy, modify, and distribute this software and its
+# documentation for any purpose, without fee, and without a written agreement
+# is hereby granted, provided that the above copyright notice and this
+# paragraph and the following two paragraphs appear in all copies.
+#
+# IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+# DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+# LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+# DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+# AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+# ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+# PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+#
+
+use strict;
+use warnings;
+use utf8;
+use open IO => ':utf8', ':std';
+use Data::Dumper;
+
+die "Usage: $0 OUTPUT_FILE\n" if @ARGV != 1;
+my $output_file = $ARGV[0];
+
+# Open the output file
+open my $OUTPUT, '>', $output_file
+  or die "Could not open output file $output_file: $!\n";
+
+# Parse code table and generate tree for letter transitions.
+my %codes;
+my %alternates;
+my $table = [{}, [["","",""]]];
+while (<DATA>) {
+	chomp;
+	my ($letters, $codes) = split(/\s+/);
+	my @codes = map { [ split(/,/) ] } split(/\|/, $codes);
+
+	# Find alternate code transitions for calculation of storage.
+	# The first character ("start of a name") can never yield more than two alternate codes,
+	# and is not considered here.
+	if (@codes > 1) {
+		for my $j (1..2) {  # Codes for "before a vowel" and "any other"
+			for my $i (0..1) {  # Alternate codes
+				# Identical code digits for adjacent letters are collapsed.
+				# For each possible non-transition due to code digit
+				# collapsing, find all alternate transitions.
+				my ($present, $next) = ($codes[$i][$j], $codes[($i + 1)%2][$j]);
+				next if length($present) != 1;
+				$next = $present ne substr($next, 0, 1) ? substr($next, 0, 1) : substr($next, -1, 1);
+				$alternates{$present}{$next} = 1;
+			}
+		}
+	}
+	my $key = "codes_" . join("_or_", map { join("_", @$_) } @codes);
+	my $val = join(",\n", map { "\t{\n\t\t" . join(", ", map { "\"$_\"" } @$_) . "\n\t}" } @codes);
+	$codes{$key} = $val;
+
+	for my $letter (split(/,/, $letters)) {
+		my $ref = $table->[0];
+		# Link each character to the next in the letter combination.
+		my @c = split(//, $letter);
+		my $last_c = pop(@c);
+		for my $c (@c) {
+			$ref->{$c} //= [ {}, undef ];
+			$ref->{$c}[0] //= {};
+			$ref = $ref->{$c}[0];
+		}
+		# The sound code for the letter combination is stored at the last character.
+		$ref->{$last_c}[1] = $key;
+	}
+}
+close(DATA);
+
+# Add alternates by following transitions to 'X' (not coded).
+my $alt_x = $alternates{"X"};
+delete $alt_x->{"X"};
+while (my ($k, $v) = each %alternates) {
+	if (delete $v->{"X"}) {
+		for my $x (keys %$alt_x) {
+			$v->{$x} = 1;
+		}
+	}
+}
+
+# Find the maximum number of alternate codes in one position.
+# Add two for any additional final code digit transitions.
+my $max_alt = (sort { $b <=> $a } (map { scalar keys %$_ } values %alternates))[0] + 2;
+
+print $OUTPUT <<EOF;
+/*
+ * Constants and lookup tables for Daitch-Mokotoff Soundex
+ *
+ * Copyright (c) 2021 Finance Norway
+ * Author: Dag Lem <dag\@nimrod.no>
+ *
+ * This file is generated by daitch_mokotoff_header.pl
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose, without fee, and without a written agreement
+ * is hereby granted, provided that the above copyright notice and this
+ * paragraph and the following two paragraphs appear in all copies.
+ *
+ * IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
+ * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
+ * DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIM ANY WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
+ * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#define DM_MAX_ALTERNATE_CODES $max_alt
+
+/* Codes for letter sequence at start of name, before a vowel, and any other. */
+EOF
+
+for my $key (sort keys %codes) {
+	print $OUTPUT "static const dm_codes $key\[2\] =\n{\n" . $codes{$key} . "\n};\n";
+}
+
+print $OUTPUT <<EOF;
+
+/* Coding for alternative following letters in sequence. */
+EOF
+
+sub hash2code {
+	my ($ref, $letter) = @_;
+
+	my @letters = ();
+
+	my $h = $ref->[0];
+	for my $key (sort keys %$h) {
+		$ref = $h->{$key};
+		my $children = "NULL";
+		if (defined $ref->[0]) {
+			$children = "letter_$letter$key";
+			hash2code($ref, "$letter$key");
+		}
+		my $codes = $ref->[1] // "NULL";
+		push(@letters, "\t{\n\t\t'$key', $children, $codes\n\t}");
+	}
+
+	print $OUTPUT "static const dm_letter letter_$letter\[\] =\n{\n";
+	for (@letters) {
+		print $OUTPUT "$_,\n";
+	}
+	print $OUTPUT "\t{\n\t\t'\\0'\n\t}\n";
+	print $OUTPUT "};\n";
+}
+
+hash2code($table, '');
+
+close $OUTPUT;
+
+# Table adapted from https://www.jewishgen.org/InfoFiles/Soundex.html
+#
+# The conversion from the coding chart to the table should be self
+# explanatory, but note the differences stated below.
+#
+# X = NC (not coded)
+#
+# The non-ASCII letters in the coding chart are coded with substitute
+# lowercase ASCII letters, which sort after the uppercase ASCII letters:
+#
+# Ą => a (use '[' for table lookup)
+# Ę => e (use '\\' for table lookup)
+# Ţ => t (use ']' for table lookup)
+#
+# The rule for "UE" does not correspond to the coding chart, however
+# it is used by all other known implementations, including the one at
+# https://www.jewishgen.org/jos/jossound.htm (try e.g. "bouey").
+#
+# Note that the implementation assumes that vowels are assigned code
+# 0 or 1. "J" can be either a vowel or a consonant.
+#
+
+__DATA__
+AI,AJ,AY				0,1,X
+AU						0,7,X
+a						X,X,6|X,X,X
+A						0,X,X
+B						7,7,7
+CHS						5,54,54
+CH						5,5,5|4,4,4
+CK						5,5,5|45,45,45
+CZ,CS,CSZ,CZS			4,4,4
+C						5,5,5|4,4,4
+DRZ,DRS					4,4,4
+DS,DSH,DSZ				4,4,4
+DZ,DZH,DZS				4,4,4
+D,DT					3,3,3
+EI,EJ,EY				0,1,X
+EU						1,1,X
+e						X,X,6|X,X,X
+E						0,X,X
+FB						7,7,7
+F						7,7,7
+G						5,5,5
+H						5,5,X
+IA,IE,IO,IU				1,X,X
+I						0,X,X
+J						1,X,X|4,4,4
+KS						5,54,54
+KH						5,5,5
+K						5,5,5
+L						8,8,8
+MN						66,66,66
+M						6,6,6
+NM						66,66,66
+N						6,6,6
+OI,OJ,OY				0,1,X
+O						0,X,X
+P,PF,PH					7,7,7
+Q						5,5,5
+RZ,RS					94,94,94|4,4,4
+R						9,9,9
+SCHTSCH,SCHTSH,SCHTCH	2,4,4
+SCH						4,4,4
+SHTCH,SHCH,SHTSH		2,4,4
+SHT,SCHT,SCHD			2,43,43
+SH						4,4,4
+STCH,STSCH,SC			2,4,4
+STRZ,STRS,STSH			2,4,4
+ST						2,43,43
+SZCZ,SZCS				2,4,4
+SZT,SHD,SZD,SD			2,43,43
+SZ						4,4,4
+S						4,4,4
+TCH,TTCH,TTSCH			4,4,4
+TH						3,3,3
+TRZ,TRS					4,4,4
+TSCH,TSH				4,4,4
+TS,TTS,TTSZ,TC			4,4,4
+TZ,TTZ,TZS,TSZ			4,4,4
+t						3,3,3|4,4,4
+T						3,3,3
+UI,UJ,UY,UE				0,1,X
+U						0,X,X
+V						7,7,7
+W						7,7,7
+X						5,54,54
+Y						1,X,X
+ZDZ,ZDZH,ZHDZH			2,4,4
+ZD,ZHD					2,43,43
+ZH,ZS,ZSCH,ZSH			4,4,4
+Z						4,4,4
diff --git a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
index 493c95cdfa..f62ddad4ee 100644
--- a/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
+++ b/contrib/fuzzystrmatch/expected/fuzzystrmatch.out
@@ -65,3 +65,174 @@ SELECT dmetaphone_alt('gumbo');
  KMP
 (1 row)
 
+-- Wovels
+SELECT daitch_mokotoff('Augsburg');
+ daitch_mokotoff 
+-----------------
+ 054795
+(1 row)
+
+SELECT daitch_mokotoff('Breuer');
+ daitch_mokotoff 
+-----------------
+ 791900
+(1 row)
+
+SELECT daitch_mokotoff('Freud');
+ daitch_mokotoff 
+-----------------
+ 793000
+(1 row)
+
+-- The letter "H"
+SELECT daitch_mokotoff('Halberstadt');
+ daitch_mokotoff 
+-----------------
+ 587943 587433
+(1 row)
+
+SELECT daitch_mokotoff('Mannheim');
+ daitch_mokotoff 
+-----------------
+ 665600
+(1 row)
+
+-- Adjacent sounds
+SELECT daitch_mokotoff('Chernowitz');
+ daitch_mokotoff 
+-----------------
+ 596740 496740
+(1 row)
+
+-- Adjacent letters with identical adjacent code digits
+SELECT daitch_mokotoff('Cherkassy');
+ daitch_mokotoff 
+-----------------
+ 595400 495400
+(1 row)
+
+SELECT daitch_mokotoff('Kleinman');
+ daitch_mokotoff 
+-----------------
+ 586660
+(1 row)
+
+-- More than one word
+SELECT daitch_mokotoff('Nowy Targ');
+ daitch_mokotoff 
+-----------------
+ 673950
+(1 row)
+
+-- Padded with "0"
+SELECT daitch_mokotoff('Berlin');
+ daitch_mokotoff 
+-----------------
+ 798600
+(1 row)
+
+-- Other examples from https://www.avotaynu.com/soundex.htm
+SELECT daitch_mokotoff('Ceniow');
+ daitch_mokotoff 
+-----------------
+ 567000 467000
+(1 row)
+
+SELECT daitch_mokotoff('Tsenyuv');
+ daitch_mokotoff 
+-----------------
+ 467000
+(1 row)
+
+SELECT daitch_mokotoff('Holubica');
+ daitch_mokotoff 
+-----------------
+ 587500 587400
+(1 row)
+
+SELECT daitch_mokotoff('Golubitsa');
+ daitch_mokotoff 
+-----------------
+ 587400
+(1 row)
+
+SELECT daitch_mokotoff('Przemysl');
+ daitch_mokotoff 
+-----------------
+ 794648 746480
+(1 row)
+
+SELECT daitch_mokotoff('Pshemeshil');
+ daitch_mokotoff 
+-----------------
+ 746480
+(1 row)
+
+SELECT daitch_mokotoff('Rosochowaciec');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 945755 945754 945745 945744 944755 944754 944745 944744
+(1 row)
+
+SELECT daitch_mokotoff('Rosokhovatsets');
+ daitch_mokotoff 
+-----------------
+ 945744
+(1 row)
+
+-- Ignored characters
+SELECT daitch_mokotoff('''OBrien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+SELECT daitch_mokotoff('O''Brien');
+ daitch_mokotoff 
+-----------------
+ 079600
+(1 row)
+
+-- "Difficult" cases, likely to cause trouble for other implementations.
+SELECT daitch_mokotoff('CJC');
+              daitch_mokotoff              
+-------------------------------------------
+ 550000 540000 545000 450000 400000 440000
+(1 row)
+
+SELECT daitch_mokotoff('BESST');
+ daitch_mokotoff 
+-----------------
+ 743000
+(1 row)
+
+SELECT daitch_mokotoff('BOUEY');
+ daitch_mokotoff 
+-----------------
+ 710000
+(1 row)
+
+SELECT daitch_mokotoff('HANNMANN');
+ daitch_mokotoff 
+-----------------
+ 566600
+(1 row)
+
+SELECT daitch_mokotoff('MCCOYJR');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 651900 654900 654190 654490 645190 645490 641900 644900
+(1 row)
+
+SELECT daitch_mokotoff('ACCURSO');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 059400 054000 054940 054400 045940 045400 049400 044000
+(1 row)
+
+SELECT daitch_mokotoff('BIERSCHBACH');
+                     daitch_mokotoff                     
+---------------------------------------------------------
+ 794575 794574 794750 794740 745750 745740 747500 747400
+(1 row)
+
diff --git a/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8.out b/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8.out
new file mode 100644
index 0000000000..32d8260383
--- /dev/null
+++ b/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8.out
@@ -0,0 +1,61 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+set client_encoding = utf8;
+-- CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
+-- Accents
+SELECT daitch_mokotoff('Müller');
+ daitch_mokotoff 
+-----------------
+ 689000
+(1 row)
+
+SELECT daitch_mokotoff('Schäfer');
+ daitch_mokotoff 
+-----------------
+ 479000
+(1 row)
+
+SELECT daitch_mokotoff('Straßburg');
+ daitch_mokotoff 
+-----------------
+ 294795
+(1 row)
+
+SELECT daitch_mokotoff('Éregon');
+ daitch_mokotoff 
+-----------------
+ 095600
+(1 row)
+
+-- Special characters added at https://www.jewishgen.org/InfoFiles/Soundex.html
+SELECT daitch_mokotoff('gąszczu');
+ daitch_mokotoff 
+-----------------
+ 564000 540000
+(1 row)
+
+SELECT daitch_mokotoff('brzęczy');
+       daitch_mokotoff       
+-----------------------------
+ 794640 794400 746400 744000
+(1 row)
+
+SELECT daitch_mokotoff('ţamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
+SELECT daitch_mokotoff('țamas');
+ daitch_mokotoff 
+-----------------
+ 364000 464000
+(1 row)
+
diff --git a/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8_1.out b/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8_1.out
new file mode 100644
index 0000000000..37aead89c0
--- /dev/null
+++ b/contrib/fuzzystrmatch/expected/fuzzystrmatch_utf8_1.out
@@ -0,0 +1,8 @@
+/*
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+ */
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql b/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql
new file mode 100644
index 0000000000..b9d7b229a3
--- /dev/null
+++ b/contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql
@@ -0,0 +1,8 @@
+/* contrib/fuzzystrmatch/fuzzystrmatch--1.1--1.2.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION fuzzystrmatch UPDATE TO '1.2'" to load this file. \quit
+
+CREATE FUNCTION daitch_mokotoff(text) RETURNS text
+AS 'MODULE_PATHNAME', 'daitch_mokotoff'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch.control b/contrib/fuzzystrmatch/fuzzystrmatch.control
index 3cd6660bf9..8b6e9fd993 100644
--- a/contrib/fuzzystrmatch/fuzzystrmatch.control
+++ b/contrib/fuzzystrmatch/fuzzystrmatch.control
@@ -1,6 +1,6 @@
 # fuzzystrmatch extension
 comment = 'determine similarities and distance between strings'
-default_version = '1.1'
+default_version = '1.2'
 module_pathname = '$libdir/fuzzystrmatch'
 relocatable = true
 trusted = true
diff --git a/contrib/fuzzystrmatch/meson.build b/contrib/fuzzystrmatch/meson.build
index e6d06149ce..6b4a13694f 100644
--- a/contrib/fuzzystrmatch/meson.build
+++ b/contrib/fuzzystrmatch/meson.build
@@ -1,7 +1,16 @@
 fuzzystrmatch_sources = files(
-  'fuzzystrmatch.c',
+  'daitch_mokotoff.c',
   'dmetaphone.c',
+  'fuzzystrmatch.c',
+)
+
+daitch_mokotoff_h = custom_target('daitch_mokotoff',
+  input: 'daitch_mokotoff_header.pl',
+  output: 'daitch_mokotoff.h',
+  command: [perl, '@INPUT@', '@OUTPUT@'],
 )
+generated_sources += daitch_mokotoff_h
+fuzzystrmatch_sources += daitch_mokotoff_h
 
 if host_system == 'windows'
   fuzzystrmatch_sources += rc_lib_gen.process(win32ver_rc, extra_args: [
@@ -19,6 +28,7 @@ install_data(
   'fuzzystrmatch.control',
   'fuzzystrmatch--1.0--1.1.sql',
   'fuzzystrmatch--1.1.sql',
+  'fuzzystrmatch--1.1--1.2.sql',
   kwargs: contrib_data_args,
 )
 
@@ -29,6 +39,7 @@ tests += {
   'regress': {
     'sql': [
       'fuzzystrmatch',
+      'fuzzystrmatch_utf8',
     ],
   },
 }
diff --git a/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql b/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
index f05dc28ffb..db05c7d6b6 100644
--- a/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
+++ b/contrib/fuzzystrmatch/sql/fuzzystrmatch.sql
@@ -19,3 +19,48 @@ SELECT metaphone('GUMBO', 4);
 
diff --git a/contrib/fuzzystrmatch/sql/fuzzystrmatch_utf8.sql b/contrib/fuzzystrmatch/sql/fuzzystrmatch_utf8.sql
index 0000000000..f42c01a1bb
+++ b/contrib/fuzzystrmatch/sql/fuzzystrmatch_utf8.sql
@@ -0,0 +1,26 @@
+ * This test must be run in a database with UTF-8 encoding,
+ * because other encodings don't support all the characters used.
+SELECT getdatabaseencoding() <> 'UTF8'
+       AS skip_test \gset
+\if :skip_test
+\quit
+\endif
+set client_encoding = utf8;
+-- CREATE EXTENSION IF NOT EXISTS fuzzystrmatch;
 
+ <sect2>

---

From: Dag Lem <[email-masked]>
Date: Thu, 22 Dec 2022 13:00:43 +0100

I noticed that the Meson builds failed in Cfbot, the updated patch adds
a missing "include_directories" line to meson.build.

Best regards

Dag Lem

 
-REGRESS = fuzzystrmatch
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
 
+-- Wovels
index e6d06149ce..73178794c2 100644
 
@@ -11,6 +20,7 @@ endif
 
 fuzzystrmatch = shared_module('fuzzystrmatch',
   fuzzystrmatch_sources,
+  include_directories: include_directories('.'),
   kwargs: contrib_mod_args,
 )
 contrib_targets += fuzzystrmatch
@@ -19,6 +29,7 @@ install_data(
   'fuzzystrmatch.control',
   'fuzzystrmatch--1.0--1.1.sql',
   'fuzzystrmatch--1.1.sql',
+  'fuzzystrmatch--1.1--1.2.sql',
   kwargs: contrib_data_args,
 )
 
@@ -29,6 +40,7 @@ tests += {
   'regress': {
     'sql': [
       'fuzzystrmatch',
+      'fuzzystrmatch_utf8',
     ],
   },
 }

+ <sect2>

---

From: Dag Lem <[email-masked]>
Date: Thu, 22 Dec 2022 14:27:54 +0100

> a missing "include_directories" line to meson.build.

This should hopefully fix the last Cfbot failures, by exclusion of
daitch_mokotoff.h from headerscheck and cpluspluscheck.

Best regards

Dag Lem

 
-REGRESS = fuzzystrmatch
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
 
+-- Wovels

 

+ <sect2>
diff --git a/src/tools/pginclude/cpluspluscheck b/src/tools/pginclude/cpluspluscheck
index b393f2a2ea..17a37aee85 100755
--- a/src/tools/pginclude/cpluspluscheck
+++ b/src/tools/pginclude/cpluspluscheck
@@ -119,6 +119,9 @@ do
 	test "$f" = src/include/common/unicode_nonspacing_table.h && continue
 	test "$f" = src/include/common/unicode_east_asian_fw_table.h && continue
 
+	# Also not meant to be included standalone.
+	test "$f" = contrib/fuzzystrmatch/daitch_mokotoff.h && continue
+
 	# We can't make these Bison output files compilable standalone
 	# without using "%code require", which old Bison versions lack.
 	# parser/gram.h will be included by parser/gramparse.h anyway.
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 2a39856f88..24aacd1239 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -114,6 +114,9 @@ do
 	test "$f" = src/include/common/unicode_nonspacing_table.h && continue
 	test "$f" = src/include/common/unicode_east_asian_fw_table.h && continue
 
+	# Also not meant to be included standalone.
+	test "$f" = contrib/fuzzystrmatch/daitch_mokotoff.h && continue
+
 	# We can't make these Bison output files compilable standalone
 	# without using "%code require", which old Bison versions lack.
 	# parser/gram.h will be included by parser/gramparse.h anyway.

---

From: Dag Lem <[email-masked]>
Date: Thu, 22 Dec 2022 15:02:54 +0100

[...]

>> I see you provided some feedback on
>> https://commitfest.postgresql.org/36/3468/,

I have scanned through all the patches in Commitfest 2023-01 with status
"Needs review", and it is difficult to find something which I can
meaningfully review.

The only thing I felt qualified to comment (or nit-pick?) on was
https://commitfest.postgresql.org/41/4071/

If something else should turn up which could be reviewed by someone
without intimate knowledge of PostgreSQL internals, then don't hesitate
to ask.

As for the Daitch-Mokotoff patch, the review by Andres Freund was very
helpful in order to improve the extension and to make it more idiomatic
- hopefully it is now a bit closer to being included.

Best regards

Dag Lem

---

From: Andres Freund <[email-masked]>
Date: Fri, 23 Dec 2022 03:22:07 -0800

> daitch_mokotoff.h from headerscheck and cpluspluscheck.

Btw, you can do the same tests as cfbot in your own repo by enabling CI
in a github repo. See src/tools/ci/README

---

From: Alvaro Herrera <[email-masked]>
Date: Fri, 23 Dec 2022 13:59:13 +0100

> daitch_mokotoff.h from headerscheck and cpluspluscheck.

Hmm, maybe it'd be better to move the typedefs to the .h file instead.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Pensar que el espectro que vemos es ilusorio no lo despoja de espanto,
sólo le suma el nuevo terror de la locura" (Perelandra, C.S. Lewis)

---

From: Alvaro Herrera <[email-masked]>
Date: Fri, 23 Dec 2022 14:07:47 +0100

I wonder why do you have it return the multiple alternative codes as a
space-separated string.  Maybe an array would be more appropriate.  Even
on your documented example use, the first thing you do is split it on
spaces.

---

From: Alvaro Herrera <[email-masked]>
Date: Fri, 23 Dec 2022 14:25:59 +0100

> on your documented example use, the first thing you do is split it on

I tried downloading a list of surnames from here
https://www.bibliotecadenombres.com/apellidos/apellidos-espanoles/
pasted that in a text file and \copy'ed it into a table.  Then I ran
this query

select string_agg(a, ' ' order by a), daitch_mokotoff(a), count(*)
from apellidos
group by daitch_mokotoff(a)
order by count(*) desc;

so I have a first entry like this

string_agg      │ Balasco Balles Belasco Belles Blas Blasco Fallas Feliz Palos Pelaez Plaza Valles Vallez Velasco Velez Veliz Veloz Villas
daitch_mokotoff │ 784000
count           │ 18

but then I have a bunch of other entries with the same code 784000 as
alternative codes,

string_agg      │ Velazco
daitch_mokotoff │ 784500 784000
count           │ 1

string_agg      │ Palacio
daitch_mokotoff │ 785000 784000
count           │ 1

I suppose I need to group these together somehow, and it would make more
sense to do that if the values were arrays.

If I scroll a bit further down and choose, say, 794000 (a relatively
popular one), then I have this

string_agg      │ Barraza Barrios Barros Bras Ferraz Frias Frisco Parras Peraza Peres Perez Porras Varas Veras
daitch_mokotoff │ 794000
count           │ 14

and looking for that code in the result I also get these three

string_agg      │ Barca Barco Parco
daitch_mokotoff │ 795000 794000
count           │ 3

string_agg      │ Borja
daitch_mokotoff │ 790000 794000
count           │ 1

string_agg      │ Borjas
daitch_mokotoff │ 794000 794400
count           │ 1

and then I see that I should also search for possible matches in codes
795000, 790000 and 794400, so that gives me

string_agg      │ Baria Baro Barrio Barro Berra Borra Feria Para Parra Perea Vera
daitch_mokotoff │ 790000
count           │ 11

string_agg      │ Barriga Borge Borrego Burgo Fraga
daitch_mokotoff │ 795000
count           │ 5

string_agg      │ Borjas
daitch_mokotoff │ 794000 794400
count           │ 1

which look closely related (compare "Veras" in the first to "Vera" in
the later set.  If you ignore that pseudo-match, you're likely to miss
possible family relationships.)

I suppose if I were a genealogy researcher, I would be helped by having
each of these codes behave as a separate unit, rather than me having to
split the string into the several possible contained values.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
"Industry suffers from the managerial dogma that for the sake of stability
and continuity, the company should be independent of the competence of
individual employees."                                      (E. Dijkstra)

---

From: Tom Lane <[email-masked]>
Date: Fri, 23 Dec 2022 09:57:13 -0500

> Hmm, maybe it'd be better to move the typedefs to the .h file instead.

Indeed, that sounds like exactly the wrong way to fix such a problem.
The bar for excluding stuff from headerscheck needs to be very high.

			regards, tom lane

---

From: Dag Lem <[email-masked]>
Date: Fri, 23 Dec 2022 21:34:09 +0100

> in a github repo. See src/tools/ci/README

OK, thanks, I've set it up now.

Best regards,

Dag Lem

---

From: Dag Lem <[email-masked]>
Date: Fri, 23 Dec 2022 21:55:11 +0100

> The bar for excluding stuff from headerscheck needs to be very high.

OK, I've moved enough declarations back to the generated header file
again so as to avoid excluding it from headerscheck and cpluspluscheck.

Best regards,

Dag Lem

 
-REGRESS = fuzzystrmatch
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
index 0000000000..e809d4a39e
@@ -0,0 +1,582 @@
index 0000000000..c5eb49a6ff
 
+-- Wovels
index 11aec733cb..abb944faaf 100644
@@ -1,9 +1,18 @@
 # Copyright (c) 2022, PostgreSQL Global Development Group

@@ -13,6 +22,7 @@ endif
 
@@ -21,6 +31,7 @@ install_data(
 
@@ -31,6 +42,7 @@ tests += {
   'regress': {
     'sql': [
       'fuzzystrmatch',
+      'fuzzystrmatch_utf8',
     ],
   },
 }

+ <sect2>

---

From: Dag Lem <[email-masked]>
Date: Fri, 23 Dec 2022 22:44:26 +0100

> on your documented example use, the first thing you do is split it on

In the example, the *input* is split on whitespace, the returned soundex
codes are not. The splitting of the input is done in order to code each
word separately. One of the stated rules of the Daitch-Mokotoff Soundex
Coding is that "When a name consists of more than one word, it is coded
as if one word", and this may not always be desired. See
https://www.avotaynu.com/soundex.htm or
https://www.jewishgen.org/InfoFiles/soundex.html for the rules.

The intended use for the Daitch-Mokotoff soundex, as for any other
soundex algorithm, is to index names (or words) on some representation
of sound, so that alike sounding names with different spellings will
match.

In PostgreSQL, the Daitch-Mokotoff Soundex and Full Text Search makes
for a powerful combination to match alike sounding names. Full Text
Search (as any other free text search engine) works with documents, and
thus the Daitch-Mokotoff Soundex implementation produces documents
(words separated by space). As stated in the documentation: "Any
alternative soundex codes are separated by space, which makes the
returned text suited for use in Full Text Search".

Best regards,

Dag Lem

---

From: Dag Lem <[email-masked]>
Date: Fri, 23 Dec 2022 23:48:02 +0100

[...]

> string_agg │ Balasco Balles Belasco Belles Blas Blasco Fallas Feliz
> Palos Pelaez Plaza Valles Vallez Velasco Velez Veliz Veloz Villas
> daitch_mokotoff │ 784000
> count           │ 18
>

It seems to me like you're trying to use soundex coding for something it
was never designed for.

As stated in my previous mail, soundex algorithms are designed to index
names on some representation of sound, so that alike sounding names with
different spellings will match, and as shown in the documentation
example, that is exactly what the implementation facilitates.

Daitch-Mokotoff Soundex indexes alternative sounds for the same name,
however if I understand correctly, you want to index names by single
sounds, linking all alike sounding names to the same soundex code. I
fail to see how that is useful - if you want to find matches for a name,
you simply match against all indexed names. If you only consider one
sound, you won't find all names that match.

In any case, as explained in the documentation, the implementation is
intended to be a companion to Full Text Search, thus text is the natural
representation for the soundex codes.

BTW Vera 790000 does not match Veras 794000, because they don't sound
the same (up to the maximum soundex code length).

Best regards

Dag Lem

---

From: Dag Lem <[email-masked]>
Date: Sat, 24 Dec 2022 08:13:07 +0100

> the same (up to the maximum soundex code length).

I've been sleeping on this, and perhaps the normal use case can just as
well (or better) be covered by the "@>" array operator? I originally
implemented similar functionality using another soundex algorithm more
than a decade ago, and either arrays couldn't be GIN indexed back then,
or I simply missed it. I'll have to get back to this - now it's
Christmas!

Merry Christmas!

Best regards,

Dag Lem

---

From: Alvaro Herrera <[email-masked]>
Date: Sun, 25 Dec 2022 14:01:36 +0100

Hello

> It seems to me like you're trying to use soundex coding for something it

I'm not trying to use it for anything, actually.  I'm just reading the
pages your patch links to, to try and understand how this algorithm can
be best implemented in Postgres.

So I got to this page
https://www.avotaynu.com/soundex.htm
which explains that Daitch figured that it would be best if a letter
that can have two possible encodings would be encoded in both ways:

> 5. If a combination of letters could have two possible sounds, then it
> is coded in both manners. For example, the letters ch can have a soft
> sound such as in Chicago or a hard sound as in Christmas.

which I understand as meaning that a single name returns two possible
encodings, which is why these three names
 Barca Barco Parco
have two possible encodings
 795000 and 794000
which is what your algorithm returns.

In fact, using the word Christmas we do get alternative codes for the first
letter (either 4 or 5), precisely as in Daitch's example:

=# select daitch_mokotoff('christmas');
 daitch_mokotoff 
─────────────────
 594364 494364
(1 fila)

and if we take out the ambiguous 'ch', we get a single one:

=# select daitch_mokotoff('ristmas');
 daitch_mokotoff 
─────────────────
 943640
(1 fila)

and if we add another 'ch', we get the codes for each possibility at each
position of the ambiguous 'ch':

=# select daitch_mokotoff('christmach');
       daitch_mokotoff       
─────────────────────────────
 594365 594364 494365 494364
(1 fila)

So, yes, I'm proposing that we returns those as array elements and that
@> is used to match them.

> sound, you won't find all names that match.

Hmm, I think we're saying the same thing, but from opposite points of
view.  No, I want each name to return multiple codes, but that those
multiple codes can be treated as a multiple-value array of codes, rather
than as a single string of space-separated codes.

> representation for the soundex codes.

Hmm, I don't agree with this point.  The numbers are representations of
the strings, but they don't necessarily have to be strings themselves.

> the same (up to the maximum soundex code length).

No, and maybe that's okay because they have different codes.  But they
are both similar, in Daitch-Mokotoff, to Borja, which has two codes,
790000 and 794000.  (Any Spanish speaker will readily tell you that
neither Vera nor Veras are similar in any way to Borja, but D-M has
chosen to say that each of them matches one of Borjas' codes.  So they
*are* related, even though indirectly, and as a genealogist you *may* be
interested in getting a match for a person called Vera when looking for
relatives to a person called Veras.  And, as a Spanish speaker, that
would make a lot of sense to me.)

Now, it's true that I've chosen to use Spanish names for my silly little
experiment.  Maybe this isn't terribly useful as a practical example,
because this algorithm seems to have been designed for Jew surnames and
perhaps not many (or not any) Jews had Spanish surnames.  I don't know;
I'm not a Jew myself (though Noah Gordon tells the tale of a Spanish Jew
called Josep Álvarez in his book "The Winemaker", so I guess it's not
impossible).  Anyway, I suspect if you repeat the experiment with names
of other origins, you'll find pretty much the same results apply there,
and that is the whole reason D-M returns multiple codes and not just
one.

Merry Christmas :-)