Subject: [PATCH v2] Add \pset options for boolean value display

From: Álvaro Herrera <[email-masked]>
Date: Mon, 20 Oct 2025 12:29:34 +0200

The server's space-expedient choice to use 't' and 'f' to represent
boolean true and false respectively is technically understandable but
visually atrocious.  Teach psql to detect these two values and print
whatever it deems is appropriate.  In the interest of backward
compatability, that defaults to 't' and 'f'.  However, now the user can
impose their own standards by using the newly introduced display_true
and display_false pset settings.

Author: David G. Johnston <[email-masked]>
Discussion: https://postgr.es/m/[email-masked]
---
 doc/src/sgml/ref/psql-ref.sgml     | 24 +++++++++++++++++
 src/bin/psql/command.c             | 43 +++++++++++++++++++++++++++++-
 src/fe_utils/print.c               |  4 +++
 src/include/fe_utils/print.h       |  2 ++
 src/test/regress/expected/psql.out | 32 ++++++++++++++++++++++
 src/test/regress/sql/psql.sql      | 16 +++++++++++
 6 files changed, 120 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 1a339600bc4..06f1e08d87a 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -3099,6 +3099,30 @@ SELECT $1 \parse stmt1
           </listitem>
           </varlistentry>
 
+          <varlistentry id="app-psql-meta-command-pset-display-false">
+          <term><literal>display_false</literal></term>
+          <listitem>
+          <para>
+          Sets the string to be printed in place of a false value.
+          The default is to print <literal>f</literal>, as that is the value
+          transmitted by the server.  For readability,
+          <literal>\pset display_false 'false'</literal> is recommended.
+          </para>
+          </listitem>
+          </varlistentry>
+
+          <varlistentry id="app-psql-meta-command-pset-display-true">
+          <term><literal>display_true</literal></term>
+          <listitem>
+          <para>
+          Sets the string to be printed in place of a true value.
+          The default is to print <literal>t</literal>, as that is the value
+          transmitted by the server.  For readability,
+          <literal>\pset display_true 'true'</literal> is recommended.
+          </para>
+          </listitem>
+          </varlistentry>
+
           <varlistentry id="app-psql-meta-command-pset-expanded">
           <term><literal>expanded</literal> (or <literal>x</literal>)</term>
           <listitem>
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index cc602087db2..f7454daf6ed 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -2709,7 +2709,8 @@ exec_command_pset(PsqlScanState scan_state, bool active_branch)
 
 			int			i;
 			static const char *const my_list[] = {
-				"border", "columns", "csv_fieldsep", "expanded", "fieldsep",
+				"border", "columns", "csv_fieldsep",
+				"display_false", "display_true", "expanded", "fieldsep",
 				"fieldsep_zero", "footer", "format", "linestyle", "null",
 				"numericlocale", "pager", "pager_min_lines",
 				"recordsep", "recordsep_zero",
@@ -5300,6 +5301,26 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
 		}
 	}
 
+	/* 'false' display */
+	else if (strcmp(param, "display_false") == 0)
+	{
+		if (value)
+		{
+			free(popt->falsePrint);
+			popt->falsePrint = pg_strdup(value);
+		}
+	}
+
+	/* 'true' display */
+	else if (strcmp(param, "display_true") == 0)
+	{
+		if (value)
+		{
+			free(popt->truePrint);
+			popt->truePrint = pg_strdup(value);
+		}
+	}
+
 	/* field separator for unaligned text */
 	else if (strcmp(param, "fieldsep") == 0)
 	{
@@ -5474,6 +5495,20 @@ printPsetInfo(const char *param, printQueryOpt *popt)
 			   popt->topt.csvFieldSep);
 	}
 
+	/* show boolean 'false' display */
+	else if (strcmp(param, "display_false") == 0)
+	{
+		printf(_("Boolean false display is \"%s\".\n"),
+			   popt->falsePrint ? popt->falsePrint : "f");
+	}
+
+	/* show boolean 'true' display */
+	else if (strcmp(param, "display_true") == 0)
+	{
+		printf(_("Boolean true display is \"%s\".\n"),
+			   popt->truePrint ? popt->truePrint : "t");
+	}
+
 	/* show field separator for unaligned text */
 	else if (strcmp(param, "fieldsep") == 0)
 	{
@@ -5743,6 +5778,12 @@ pset_value_string(const char *param, printQueryOpt *popt)
 		return psprintf("%d", popt->topt.columns);
 	else if (strcmp(param, "csv_fieldsep") == 0)
 		return pset_quoted_string(popt->topt.csvFieldSep);
+	else if (strcmp(param, "display_false") == 0)
+		return pset_quoted_string(popt->falsePrint ?
+								  popt->falsePrint : "f");
+	else if (strcmp(param, "display_true") == 0)
+		return pset_quoted_string(popt->truePrint ?
+								  popt->truePrint : "t");
 	else if (strcmp(param, "expanded") == 0)
 		return pstrdup(popt->topt.expanded == 2
 					   ? "auto"
diff --git a/src/fe_utils/print.c b/src/fe_utils/print.c
index 73847d3d6b3..4d97ad2ddeb 100644
--- a/src/fe_utils/print.c
+++ b/src/fe_utils/print.c
@@ -3775,6 +3775,10 @@ printQuery(const PGresult *result, const printQueryOpt *opt,
 
 			if (PQgetisnull(result, r, c))
 				cell = opt->nullPrint ? opt->nullPrint : "";
+			else if (PQftype(result, c) == BOOLOID)
+				cell = (PQgetvalue(result, r, c)[0] == 't' ?
+						(opt->truePrint ? opt->truePrint : "t") :
+						(opt->falsePrint ? opt->falsePrint : "f"));
 			else
 			{
 				cell = PQgetvalue(result, r, c);
diff --git a/src/include/fe_utils/print.h b/src/include/fe_utils/print.h
index c99c2ee1a31..6a6fc7e132c 100644
--- a/src/include/fe_utils/print.h
+++ b/src/include/fe_utils/print.h
@@ -184,6 +184,8 @@ typedef struct printQueryOpt
 {
 	printTableOpt topt;			/* the options above */
 	char	   *nullPrint;		/* how to print null entities */
+	char	   *truePrint;		/* how to print boolean true values */
+	char	   *falsePrint;		/* how to print boolean false values */
 	char	   *title;			/* override title */
 	char	  **footers;		/* override footer (default is "(xx rows)") */
 	bool		translate_header;	/* do gettext on column headers */
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index fa8984ffe0d..c8f3932edf0 100644
--- a/src/test/regress/expected/psql.out
+++ b/src/test/regress/expected/psql.out
@@ -445,6 +445,8 @@ environment value
 border                   1
 columns                  0
 csv_fieldsep             ','
+display_false            'f'
+display_true             't'
 expanded                 off
 fieldsep                 '|'
 fieldsep_zero            off
@@ -464,6 +466,36 @@ unicode_border_linestyle single
 unicode_column_linestyle single
 unicode_header_linestyle single
 xheader_width            full
+-- test the simple display substitution settings
+prepare q as select null as n, true as t, false as f;
+\pset null '(null)'
+\pset display_true 'true'
+\pset display_false 'false'
+execute q;
+   n    |  t   |   f   
+--------+------+-------
+ (null) | true | false
+(1 row)
+
+\pset null
+\pset display_true
+\pset display_false
+execute q;
+   n    |  t   |   f   
+--------+------+-------
+ (null) | true | false
+(1 row)
+
+\pset null ''
+\pset display_true 't'
+\pset display_false 'f'
+execute q;
+ n | t | f 
+---+---+---
+   | t | f
+(1 row)
+
+deallocate q;
 -- test multi-line headers, wrapping, and newline indicators
 -- in aligned, unaligned, and wrapped formats
 prepare q as select array_to_string(array_agg(repeat('x',2*n)),E'\n') as "ab
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index f064e4f5456..dcdbd4fc020 100644
--- a/src/test/regress/sql/psql.sql
+++ b/src/test/regress/sql/psql.sql
@@ -219,6 +219,22 @@ select 'drop table gexec_test', 'select ''2000-01-01''::date as party_over'
 -- show all pset options
 \pset
 
+-- test the simple display substitution settings
+prepare q as select null as n, true as t, false as f;
+\pset null '(null)'
+\pset display_true 'true'
+\pset display_false 'false'
+execute q;
+\pset null
+\pset display_true
+\pset display_false
+execute q;
+\pset null ''
+\pset display_true 't'
+\pset display_false 'f'
+execute q;
+deallocate q;
+
 -- test multi-line headers, wrapping, and newline indicators
 -- in aligned, unaligned, and wrapped formats
 prepare q as select array_to_string(array_agg(repeat('x',2*n)),E'\n') as "ab
-- 
2.47.3

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