public inbox for [email protected]
help / color / mirror / Atom feedFrom: Sami Imseih <[email protected]>
To: Lukas Fittl <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: zengman <[email protected]>
Cc: pgsql-hackers <[email protected]>
Cc: Julien Rouhaud <[email protected]>
Subject: Re: Refactor query normalization into core query jumbling
Date: Tue, 6 Jan 2026 14:20:47 -0600
Message-ID: <CAA5RZ0t_CJs9ye1PPBy-e0ajZ-6FgKvNEoacW9keCtF_7Y2ycQ@mail.gmail.com> (raw)
In-Reply-To: <CAA5RZ0t3-srmtaVNfzv0HEzXCa78eQDKYVak+3zgEccnKPZHHA@mail.gmail.com>
References: <CAA5RZ0tZp5qU0ikZEEqJnxvdSNGh1DWv80sb-k4QAUmiMoOp_Q@mail.gmail.com>
<[email protected]>
<CAA5RZ0vQfE14HyfpoPXDRThVcdCkLgY_HGz+J2qLB9soNUE9QQ@mail.gmail.com>
<[email protected]>
<CAA5RZ0uLS9RrpO2roX7p3EHE4-VJkBsGAB970jrbo1-GRDAi0g@mail.gmail.com>
<[email protected]>
<CAA5RZ0sbWmqdUBFo8JXMJe72pnwjxVY58htJ6pKbwnyQuRctQw@mail.gmail.com>
<CAP53PkxqGbPw5VzpacyJb2wTofYJadCoUmxV8s2o5tHzKznwbg@mail.gmail.com>
<CAA5RZ0t3-srmtaVNfzv0HEzXCa78eQDKYVak+3zgEccnKPZHHA@mail.gmail.com>
> >> backwards compatible. Basically, we keep JumbleState a non-constant,
> >> but provide core APIs for any operation, such as
> >> generate_normalized_query,
> >> that needs to modify the state. So, my approach was not about enforcing a
> >> read-only JumbleState, but about providing the API to dissuade an author
> >> from modifying a JumbleState.
>
> > Given the lack of public APIs to modify JumbleState today, I don't see how
> > an extension would do
> > modifications in a meaningful way, short of copying the code. I think we
> > should be a bit bolder here in
> > enforcing a convention, either clearly making it read-only or dropping the
> > argument again.
>
> Based on the discussion so far I am leaning towards making JumbleState
> read-only as described here [0]. I don't see how we can drop JumbleState
> completely from hooks, since normalization needs to occur on-demand
> by the extension.
Here is v4.
0001 - addresses the comments made by Bertrand.
0002 - makes JumbleState a constant when passed to post_parse_analyze
and updates all downstream code that consume the JumbleState. This
means we now need to copy the locations from JState into a local/temporary
array when generating the normalized string.
--
Sami Imseih
Amazon Web Services (AWS)
Attachments:
[application/octet-stream] v4-0002-Make-JumbleState-const-in-post_parse_analyze-hook.patch (8.5K, 2-v4-0002-Make-JumbleState-const-in-post_parse_analyze-hook.patch)
download | inline diff:
From 12575c2db5ccfc070b4024d644e4c72e32497486 Mon Sep 17 00:00:00 2001
From: Ubuntu <[email protected]>
Date: Tue, 6 Jan 2026 19:29:01 +0000
Subject: [PATCH v4 2/2] Make JumbleState const in post_parse_analyze hook
Change the post_parse_analyze_hook_type signature to take a const
JumbleState parameter, preventing hooks from modifying the jumble
state during query analysis. This improves API safety by making it
clear that hooks should only read from the jumble state, not modify
it.
Update pg_stat_statements and related functions to match the new const
signature. Refactor SetConstantLengths() to return a newly allocated
LocationLen array instead of modifying the JumbleState, and update
GenerateNormalizedQuery() to work with the const JumbleState and
manage the returned array properly.
Discussion: https://postgr.es/m/CAA5RZ0tZp5qU0ikZEEqJnxvdSNGh1DWv80sb-k4QAUmiMoOp_Q@mail.gmail.com
---
.../pg_stat_statements/pg_stat_statements.c | 8 ++--
src/backend/nodes/queryjumblefuncs.c | 39 +++++++++++++------
src/include/nodes/queryjumble.h | 2 +-
src/include/parser/analyze.h | 2 +-
4 files changed, 33 insertions(+), 18 deletions(-)
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index b90891859d9..b796d839cec 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -332,7 +332,7 @@ static void pgss_shmem_request(void);
static void pgss_shmem_startup(void);
static void pgss_shmem_shutdown(int code, Datum arg);
static void pgss_post_parse_analyze(ParseState *pstate, Query *query,
- JumbleState *jstate);
+ const JumbleState *jstate);
static PlannedStmt *pgss_planner(Query *parse,
const char *query_string,
int cursorOptions,
@@ -356,7 +356,7 @@ static void pgss_store(const char *query, int64 queryId,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
- JumbleState *jstate,
+ const JumbleState *jstate,
int parallel_workers_to_launch,
int parallel_workers_launched,
PlannedStmtOrigin planOrigin);
@@ -832,7 +832,7 @@ error:
* Post-parse-analysis hook: mark query with a queryId
*/
static void
-pgss_post_parse_analyze(ParseState *pstate, Query *query, JumbleState *jstate)
+pgss_post_parse_analyze(ParseState *pstate, Query *query, const JumbleState *jstate)
{
if (prev_post_parse_analyze_hook)
prev_post_parse_analyze_hook(pstate, query, jstate);
@@ -1289,7 +1289,7 @@ pgss_store(const char *query, int64 queryId,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
- JumbleState *jstate,
+ const JumbleState *jstate,
int parallel_workers_to_launch,
int parallel_workers_launched,
PlannedStmtOrigin planOrigin)
diff --git a/src/backend/nodes/queryjumblefuncs.c b/src/backend/nodes/queryjumblefuncs.c
index dd53c82b2a8..4dfe9087547 100644
--- a/src/backend/nodes/queryjumblefuncs.c
+++ b/src/backend/nodes/queryjumblefuncs.c
@@ -789,8 +789,10 @@ CompLocation(const void *a, const void *b)
}
/*
- * Given a valid SQL string and an array of constant-location records,
- * fill in the textual lengths of those constants in JumbleState.
+ * Given a valid SQL string and an array of constant-location records, return
+ * the textual lengths of those constants in a newly allocated LocationLen
+ * array, or NULL if there are no constants. It is the caller's responsibility
+ * to pfree the result, if necessary.
*
* The constants may use any allowed constant syntax, such as float literals,
* bit-strings, single-quoted strings and dollar-quoted strings. This is
@@ -803,8 +805,8 @@ CompLocation(const void *a, const void *b)
* a negative numeric constant. This precludes there ever being another
* reason for a constant to start with a '-'.
*/
-static void
-SetConstantLengths(JumbleState *jstate, const char *query,
+static LocationLen *
+SetConstantLengths(const JumbleState *jstate, const char *query,
int query_loc)
{
LocationLen *locs;
@@ -813,14 +815,20 @@ SetConstantLengths(JumbleState *jstate, const char *query,
core_YYSTYPE yylval;
YYLTYPE yylloc;
+ if (jstate->clocations_count == 0)
+ return NULL;
+
+ /* Copy constant locations to avoid modifying jstate */
+ locs = palloc(jstate->clocations_count * sizeof(LocationLen));
+ memcpy(locs, jstate->clocations, jstate->clocations_count * sizeof(LocationLen));
+
/*
* Sort the records by location so that we can process them in order while
* scanning the query text.
*/
if (jstate->clocations_count > 1)
- qsort(jstate->clocations, jstate->clocations_count,
+ qsort(locs, jstate->clocations_count,
sizeof(LocationLen), CompLocation);
- locs = jstate->clocations;
/* initialize the flex scanner --- should match raw_parser() */
yyscanner = scanner_init(query,
@@ -908,6 +916,8 @@ SetConstantLengths(JumbleState *jstate, const char *query,
}
scanner_finish(yyscanner);
+
+ return locs;
}
/*
@@ -926,7 +936,7 @@ SetConstantLengths(JumbleState *jstate, const char *query,
* Returns a palloc'd string.
*/
char *
-GenerateNormalizedQuery(JumbleState *jstate, const char *query,
+GenerateNormalizedQuery(const JumbleState *jstate, const char *query,
int query_loc, int *query_len_p)
{
char *norm_query;
@@ -938,12 +948,13 @@ GenerateNormalizedQuery(JumbleState *jstate, const char *query,
last_off = 0, /* Offset from start for previous tok */
last_tok_len = 0; /* Length (in bytes) of that tok */
int num_constants_replaced = 0;
+ LocationLen *locs = NULL;
/*
* Set constants' lengths in JumbleState, as only locations are set during
* DoJumble(). Note this also ensures the items are sorted by location.
*/
- SetConstantLengths(jstate, query, query_loc);
+ locs = SetConstantLengths(jstate, query, query_loc);
/*
* Allow for $n symbols to be longer than the constants they replace.
@@ -969,15 +980,15 @@ GenerateNormalizedQuery(JumbleState *jstate, const char *query,
* the parameter in the next iteration (or after the loop is done),
* which is a bit odd but seems to work okay in most cases.
*/
- if (jstate->clocations[i].extern_param && !jstate->has_squashed_lists)
+ if (locs[i].extern_param && !jstate->has_squashed_lists)
continue;
- off = jstate->clocations[i].location;
+ off = locs[i].location;
/* Adjust the constant's location (see SetConstantLengths) */
off -= query_loc;
- tok_len = jstate->clocations[i].length;
+ tok_len = locs[i].length;
if (tok_len < 0)
continue; /* ignore any duplicates */
@@ -996,7 +1007,7 @@ GenerateNormalizedQuery(JumbleState *jstate, const char *query,
*/
n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d%s",
num_constants_replaced + 1 + jstate->highest_extern_param_id,
- jstate->clocations[i].squashed ? " /*, ... */" : "");
+ locs[i].squashed ? " /*, ... */" : "");
num_constants_replaced++;
/* move forward */
@@ -1005,6 +1016,10 @@ GenerateNormalizedQuery(JumbleState *jstate, const char *query,
last_tok_len = tok_len;
}
+ /* Clean up temporary location array before any assertions */
+ if (locs)
+ pfree(locs);
+
/*
* We've copied up until the last ignorable constant. Copy over the
* remaining bytes of the original query string.
diff --git a/src/include/nodes/queryjumble.h b/src/include/nodes/queryjumble.h
index cb8741b1d05..bc3dc4d846f 100644
--- a/src/include/nodes/queryjumble.h
+++ b/src/include/nodes/queryjumble.h
@@ -91,7 +91,7 @@ extern PGDLLIMPORT int compute_query_id;
extern const char *CleanQuerytext(const char *query, int *location, int *len);
-extern char *GenerateNormalizedQuery(JumbleState *jstate, const char *query,
+extern char *GenerateNormalizedQuery(const JumbleState *jstate, const char *query,
int query_loc, int *query_len_p);
extern JumbleState *JumbleQuery(Query *query);
extern void EnableQueryId(void);
diff --git a/src/include/parser/analyze.h b/src/include/parser/analyze.h
index f29ed03b476..f80da72933c 100644
--- a/src/include/parser/analyze.h
+++ b/src/include/parser/analyze.h
@@ -21,7 +21,7 @@
/* Hook for plugins to get control at end of parse analysis */
typedef void (*post_parse_analyze_hook_type) (ParseState *pstate,
Query *query,
- JumbleState *jstate);
+ const JumbleState *jstate);
extern PGDLLIMPORT post_parse_analyze_hook_type post_parse_analyze_hook;
--
2.43.0
[application/octet-stream] v4-0001-pg_stat_statements-Move-query-normalization-to-co.patch (20.8K, 3-v4-0001-pg_stat_statements-Move-query-normalization-to-co.patch)
download | inline diff:
From 63741aec2ca489d066ed4cdc8f50ec36b7894ffd Mon Sep 17 00:00:00 2001
From: Ubuntu <[email protected]>
Date: Thu, 18 Dec 2025 18:59:31 +0000
Subject: [PATCH v4 1/2] pg_stat_statements: Move query normalization to core
pg_stat_statements was modifying core generated JumbleState instances
by calling fill_in_constant_lengths() via generate_normalized_query()
to populate constant lengths. This creates problems since extensions
should not modify shared core data structures that may be used by
other extensions, and this could be considered a layering violation.
Move query normalization functions to core as a global function to
fix this. Extensions now call GenerateNormalizedQuery() instead of
directly modifying JumbleState.
This change also addresses code duplication, as several extensions
have been copying generate_normalized_query() to implement their own
normalization. The new core API provides a single, consistent
implementation for all extensions to use.
Functions are renamed to match core naming conventions and comments
are updated for clarity.
Discussion: https://postgr.es/m/CAA5RZ0tZp5qU0ikZEEqJnxvdSNGh1DWv80sb-k4QAUmiMoOp_Q@mail.gmail.com
---
.../pg_stat_statements/pg_stat_statements.c | 276 +-----------------
src/backend/nodes/queryjumblefuncs.c | 248 ++++++++++++++++
src/include/nodes/queryjumble.h | 2 +
3 files changed, 260 insertions(+), 266 deletions(-)
diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 39208f80b5b..b90891859d9 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -50,7 +50,6 @@
#include "access/htup_details.h"
#include "access/parallel.h"
#include "catalog/pg_authid.h"
-#include "common/int.h"
#include "executor/instrument.h"
#include "funcapi.h"
#include "jit/jit.h"
@@ -59,7 +58,6 @@
#include "nodes/queryjumble.h"
#include "optimizer/planner.h"
#include "parser/analyze.h"
-#include "parser/scanner.h"
#include "pgstat.h"
#include "storage/fd.h"
#include "storage/ipc.h"
@@ -377,11 +375,6 @@ static char *qtext_fetch(Size query_offset, int query_len,
static bool need_gc_qtexts(void);
static void gc_qtexts(void);
static TimestampTz entry_reset(Oid userid, Oid dbid, int64 queryid, bool minmax_only);
-static char *generate_normalized_query(JumbleState *jstate, const char *query,
- int query_loc, int *query_len_p);
-static void fill_in_constant_lengths(JumbleState *jstate, const char *query,
- int query_loc);
-static int comp_location(const void *a, const void *b);
/*
@@ -1359,9 +1352,16 @@ pgss_store(const char *query, int64 queryId,
if (jstate)
{
LWLockRelease(pgss->lock);
- norm_query = generate_normalized_query(jstate, query,
- query_location,
- &query_len);
+
+ /*
+ * generate the normalized query. Note that the normalized
+ * representation may well vary depending on just which
+ * "equivalent" query is used to create the hashtable entry. We
+ * assume this is OK.
+ */
+ norm_query = GenerateNormalizedQuery(jstate, query,
+ query_location,
+ &query_len);
LWLockAcquire(pgss->lock, LW_SHARED);
}
@@ -2823,259 +2823,3 @@ release_lock:
return stats_reset;
}
-
-/*
- * Generate a normalized version of the query string that will be used to
- * represent all similar queries.
- *
- * Note that the normalized representation may well vary depending on
- * just which "equivalent" query is used to create the hashtable entry.
- * We assume this is OK.
- *
- * If query_loc > 0, then "query" has been advanced by that much compared to
- * the original string start, so we need to translate the provided locations
- * to compensate. (This lets us avoid re-scanning statements before the one
- * of interest, so it's worth doing.)
- *
- * *query_len_p contains the input string length, and is updated with
- * the result string length on exit. The resulting string might be longer
- * or shorter depending on what happens with replacement of constants.
- *
- * Returns a palloc'd string.
- */
-static char *
-generate_normalized_query(JumbleState *jstate, const char *query,
- int query_loc, int *query_len_p)
-{
- char *norm_query;
- int query_len = *query_len_p;
- int norm_query_buflen, /* Space allowed for norm_query */
- len_to_wrt, /* Length (in bytes) to write */
- quer_loc = 0, /* Source query byte location */
- n_quer_loc = 0, /* Normalized query byte location */
- last_off = 0, /* Offset from start for previous tok */
- last_tok_len = 0; /* Length (in bytes) of that tok */
- int num_constants_replaced = 0;
-
- /*
- * Get constants' lengths (core system only gives us locations). Note
- * this also ensures the items are sorted by location.
- */
- fill_in_constant_lengths(jstate, query, query_loc);
-
- /*
- * Allow for $n symbols to be longer than the constants they replace.
- * Constants must take at least one byte in text form, while a $n symbol
- * certainly isn't more than 11 bytes, even if n reaches INT_MAX. We
- * could refine that limit based on the max value of n for the current
- * query, but it hardly seems worth any extra effort to do so.
- */
- norm_query_buflen = query_len + jstate->clocations_count * 10;
-
- /* Allocate result buffer */
- norm_query = palloc(norm_query_buflen + 1);
-
- for (int i = 0; i < jstate->clocations_count; i++)
- {
- int off, /* Offset from start for cur tok */
- tok_len; /* Length (in bytes) of that tok */
-
- /*
- * If we have an external param at this location, but no lists are
- * being squashed across the query, then we skip here; this will make
- * us print the characters found in the original query that represent
- * the parameter in the next iteration (or after the loop is done),
- * which is a bit odd but seems to work okay in most cases.
- */
- if (jstate->clocations[i].extern_param && !jstate->has_squashed_lists)
- continue;
-
- off = jstate->clocations[i].location;
-
- /* Adjust recorded location if we're dealing with partial string */
- off -= query_loc;
-
- tok_len = jstate->clocations[i].length;
-
- if (tok_len < 0)
- continue; /* ignore any duplicates */
-
- /* Copy next chunk (what precedes the next constant) */
- len_to_wrt = off - last_off;
- len_to_wrt -= last_tok_len;
- Assert(len_to_wrt >= 0);
- memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
- n_quer_loc += len_to_wrt;
-
- /*
- * And insert a param symbol in place of the constant token; and, if
- * we have a squashable list, insert a placeholder comment starting
- * from the list's second value.
- */
- n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d%s",
- num_constants_replaced + 1 + jstate->highest_extern_param_id,
- jstate->clocations[i].squashed ? " /*, ... */" : "");
- num_constants_replaced++;
-
- /* move forward */
- quer_loc = off + tok_len;
- last_off = off;
- last_tok_len = tok_len;
- }
-
- /*
- * We've copied up until the last ignorable constant. Copy over the
- * remaining bytes of the original query string.
- */
- len_to_wrt = query_len - quer_loc;
-
- Assert(len_to_wrt >= 0);
- memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
- n_quer_loc += len_to_wrt;
-
- Assert(n_quer_loc <= norm_query_buflen);
- norm_query[n_quer_loc] = '\0';
-
- *query_len_p = n_quer_loc;
- return norm_query;
-}
-
-/*
- * Given a valid SQL string and an array of constant-location records,
- * fill in the textual lengths of those constants.
- *
- * The constants may use any allowed constant syntax, such as float literals,
- * bit-strings, single-quoted strings and dollar-quoted strings. This is
- * accomplished by using the public API for the core scanner.
- *
- * It is the caller's job to ensure that the string is a valid SQL statement
- * with constants at the indicated locations. Since in practice the string
- * has already been parsed, and the locations that the caller provides will
- * have originated from within the authoritative parser, this should not be
- * a problem.
- *
- * Multiple constants can have the same location. We reset lengths of those
- * past the first to -1 so that they can later be ignored.
- *
- * If query_loc > 0, then "query" has been advanced by that much compared to
- * the original string start, so we need to translate the provided locations
- * to compensate. (This lets us avoid re-scanning statements before the one
- * of interest, so it's worth doing.)
- *
- * N.B. There is an assumption that a '-' character at a Const location begins
- * a negative numeric constant. This precludes there ever being another
- * reason for a constant to start with a '-'.
- */
-static void
-fill_in_constant_lengths(JumbleState *jstate, const char *query,
- int query_loc)
-{
- LocationLen *locs;
- core_yyscan_t yyscanner;
- core_yy_extra_type yyextra;
- core_YYSTYPE yylval;
- YYLTYPE yylloc;
-
- /*
- * Sort the records by location so that we can process them in order while
- * scanning the query text.
- */
- if (jstate->clocations_count > 1)
- qsort(jstate->clocations, jstate->clocations_count,
- sizeof(LocationLen), comp_location);
- locs = jstate->clocations;
-
- /* initialize the flex scanner --- should match raw_parser() */
- yyscanner = scanner_init(query,
- &yyextra,
- &ScanKeywords,
- ScanKeywordTokens);
-
- /* we don't want to re-emit any escape string warnings */
- yyextra.escape_string_warning = false;
-
- /* Search for each constant, in sequence */
- for (int i = 0; i < jstate->clocations_count; i++)
- {
- int loc;
- int tok;
-
- /* Ignore constants after the first one in the same location */
- if (i > 0 && locs[i].location == locs[i - 1].location)
- {
- locs[i].length = -1;
- continue;
- }
-
- if (locs[i].squashed)
- continue; /* squashable list, ignore */
-
- /* Adjust recorded location if we're dealing with partial string */
- loc = locs[i].location - query_loc;
- Assert(loc >= 0);
-
- /*
- * We have a valid location for a constant that's not a dupe. Lex
- * tokens until we find the desired constant.
- */
- for (;;)
- {
- tok = core_yylex(&yylval, &yylloc, yyscanner);
-
- /* We should not hit end-of-string, but if we do, behave sanely */
- if (tok == 0)
- break; /* out of inner for-loop */
-
- /*
- * We should find the token position exactly, but if we somehow
- * run past it, work with that.
- */
- if (yylloc >= loc)
- {
- if (query[loc] == '-')
- {
- /*
- * It's a negative value - this is the one and only case
- * where we replace more than a single token.
- *
- * Do not compensate for the core system's special-case
- * adjustment of location to that of the leading '-'
- * operator in the event of a negative constant. It is
- * also useful for our purposes to start from the minus
- * symbol. In this way, queries like "select * from foo
- * where bar = 1" and "select * from foo where bar = -2"
- * will have identical normalized query strings.
- */
- tok = core_yylex(&yylval, &yylloc, yyscanner);
- if (tok == 0)
- break; /* out of inner for-loop */
- }
-
- /*
- * We now rely on the assumption that flex has placed a zero
- * byte after the text of the current token in scanbuf.
- */
- locs[i].length = strlen(yyextra.scanbuf + loc);
- break; /* out of inner for-loop */
- }
- }
-
- /* If we hit end-of-string, give up, leaving remaining lengths -1 */
- if (tok == 0)
- break;
- }
-
- scanner_finish(yyscanner);
-}
-
-/*
- * comp_location: comparator for qsorting LocationLen structs by location
- */
-static int
-comp_location(const void *a, const void *b)
-{
- int l = ((const LocationLen *) a)->location;
- int r = ((const LocationLen *) b)->location;
-
- return pg_cmp_s32(l, r);
-}
diff --git a/src/backend/nodes/queryjumblefuncs.c b/src/backend/nodes/queryjumblefuncs.c
index ffc230af427..dd53c82b2a8 100644
--- a/src/backend/nodes/queryjumblefuncs.c
+++ b/src/backend/nodes/queryjumblefuncs.c
@@ -40,10 +40,12 @@
#include "access/transam.h"
#include "catalog/pg_proc.h"
#include "common/hashfn.h"
+#include "common/int.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "nodes/queryjumble.h"
#include "utils/lsyscache.h"
+#include "parser/scanner.h"
#include "parser/scansup.h"
#define JUMBLE_SIZE 1024 /* query serialization buffer size */
@@ -773,3 +775,249 @@ _jumbleRangeTblEntry_eref(JumbleState *jstate,
*/
JUMBLE_STRING(aliasname);
}
+
+/*
+ * CompLocation: comparator for qsorting LocationLen structs by location
+ */
+static int
+CompLocation(const void *a, const void *b)
+{
+ int l = ((const LocationLen *) a)->location;
+ int r = ((const LocationLen *) b)->location;
+
+ return pg_cmp_s32(l, r);
+}
+
+/*
+ * Given a valid SQL string and an array of constant-location records,
+ * fill in the textual lengths of those constants in JumbleState.
+ *
+ * The constants may use any allowed constant syntax, such as float literals,
+ * bit-strings, single-quoted strings and dollar-quoted strings. This is
+ * accomplished by using the public API for the core scanner.
+ *
+ * Multiple constants can have the same location. We reset lengths of those
+ * past the first to -1 so that they can later be ignored.
+ *
+ * N.B. There is an assumption that a '-' character at a Const location begins
+ * a negative numeric constant. This precludes there ever being another
+ * reason for a constant to start with a '-'.
+ */
+static void
+SetConstantLengths(JumbleState *jstate, const char *query,
+ int query_loc)
+{
+ LocationLen *locs;
+ core_yyscan_t yyscanner;
+ core_yy_extra_type yyextra;
+ core_YYSTYPE yylval;
+ YYLTYPE yylloc;
+
+ /*
+ * Sort the records by location so that we can process them in order while
+ * scanning the query text.
+ */
+ if (jstate->clocations_count > 1)
+ qsort(jstate->clocations, jstate->clocations_count,
+ sizeof(LocationLen), CompLocation);
+ locs = jstate->clocations;
+
+ /* initialize the flex scanner --- should match raw_parser() */
+ yyscanner = scanner_init(query,
+ &yyextra,
+ &ScanKeywords,
+ ScanKeywordTokens);
+
+ /* we don't want to re-emit any escape string warnings */
+ yyextra.escape_string_warning = false;
+
+ /* Search for each constant, in sequence */
+ for (int i = 0; i < jstate->clocations_count; i++)
+ {
+ int loc;
+ int tok;
+
+ /* Ignore constants after the first one in the same location */
+ if (i > 0 && locs[i].location == locs[i - 1].location)
+ {
+ locs[i].length = -1;
+ continue;
+ }
+
+ if (locs[i].squashed)
+ continue; /* squashable list, ignore */
+
+ /*
+ * Adjust the constant's location using the provided starting location
+ * of the current statement. This allows us to avoid scanning a
+ * multi-statement string from the beginning.
+ */
+ loc = locs[i].location - query_loc;
+ Assert(loc >= 0);
+
+ /*
+ * We have a valid location for a constant that's not a dupe. Lex
+ * tokens until we find the desired constant.
+ */
+ for (;;)
+ {
+ tok = core_yylex(&yylval, &yylloc, yyscanner);
+
+ /* We should not hit end-of-string, but if we do, behave sanely */
+ if (tok == 0)
+ break; /* out of inner for-loop */
+
+ /*
+ * We should find the token position exactly, but if we somehow
+ * run past it, work with that.
+ */
+ if (yylloc >= loc)
+ {
+ if (query[loc] == '-')
+ {
+ /*
+ * It's a negative value - this is the one and only case
+ * where we replace more than a single token.
+ *
+ * Do not compensate for the special-case adjustment of
+ * location to that of the leading '-' operator in the
+ * event of a negative constant (see doNegate() in
+ * gram.y). It is also useful for our purposes to start
+ * from the minus symbol. In this way, queries like
+ * "select * from foo where bar = 1" and "select * from
+ * foo where bar = -2" will have identical normalized
+ * query strings.
+ */
+ tok = core_yylex(&yylval, &yylloc, yyscanner);
+ if (tok == 0)
+ break; /* out of inner for-loop */
+ }
+
+ /*
+ * We now rely on the assumption that flex has placed a zero
+ * byte after the text of the current token in scanbuf.
+ */
+ locs[i].length = strlen(yyextra.scanbuf + loc);
+ break; /* out of inner for-loop */
+ }
+ }
+
+ /* If we hit end-of-string, give up, leaving remaining lengths -1 */
+ if (tok == 0)
+ break;
+ }
+
+ scanner_finish(yyscanner);
+}
+
+/*
+ * Callback to generate a normalized version of the query string that will be used to
+ * represent all similar queries.
+ *
+ * It is the caller's job to ensure that the string is a valid SQL statement
+ * with the correct constant locations in jstate->clocations. Since in
+ * practice the string has already been parsed using the authoritative parser
+ * and the locations are set by core query jumbling, this should not be a problem.
+ *
+ * *query_len_p contains the input string length, and is updated with
+ * the result string length on exit. The resulting string might be longer
+ * or shorter depending on what happens with replacement of constants.
+ *
+ * Returns a palloc'd string.
+ */
+char *
+GenerateNormalizedQuery(JumbleState *jstate, const char *query,
+ int query_loc, int *query_len_p)
+{
+ char *norm_query;
+ int query_len = *query_len_p;
+ int norm_query_buflen, /* Space allowed for norm_query */
+ len_to_wrt, /* Length (in bytes) to write */
+ quer_loc = 0, /* Source query byte location */
+ n_quer_loc = 0, /* Normalized query byte location */
+ last_off = 0, /* Offset from start for previous tok */
+ last_tok_len = 0; /* Length (in bytes) of that tok */
+ int num_constants_replaced = 0;
+
+ /*
+ * Set constants' lengths in JumbleState, as only locations are set during
+ * DoJumble(). Note this also ensures the items are sorted by location.
+ */
+ SetConstantLengths(jstate, query, query_loc);
+
+ /*
+ * Allow for $n symbols to be longer than the constants they replace.
+ * Constants must take at least one byte in text form, while a $n symbol
+ * certainly isn't more than 11 bytes, even if n reaches INT_MAX. We
+ * could refine that limit based on the max value of n for the current
+ * query, but it hardly seems worth any extra effort to do so.
+ */
+ norm_query_buflen = query_len + jstate->clocations_count * 10;
+
+ /* Allocate result buffer */
+ norm_query = palloc(norm_query_buflen + 1);
+
+ for (int i = 0; i < jstate->clocations_count; i++)
+ {
+ int off, /* Offset from start for cur tok */
+ tok_len; /* Length (in bytes) of that tok */
+
+ /*
+ * If we have an external param at this location, but no lists are
+ * being squashed across the query, then we skip here; this will make
+ * us print the characters found in the original query that represent
+ * the parameter in the next iteration (or after the loop is done),
+ * which is a bit odd but seems to work okay in most cases.
+ */
+ if (jstate->clocations[i].extern_param && !jstate->has_squashed_lists)
+ continue;
+
+ off = jstate->clocations[i].location;
+
+ /* Adjust the constant's location (see SetConstantLengths) */
+ off -= query_loc;
+
+ tok_len = jstate->clocations[i].length;
+
+ if (tok_len < 0)
+ continue; /* ignore any duplicates */
+
+ /* Copy next chunk (what precedes the next constant) */
+ len_to_wrt = off - last_off;
+ len_to_wrt -= last_tok_len;
+ Assert(len_to_wrt >= 0);
+ memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
+ n_quer_loc += len_to_wrt;
+
+ /*
+ * And insert a param symbol in place of the constant token; and, if
+ * we have a squashable list, insert a placeholder comment starting
+ * from the list's second value.
+ */
+ n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d%s",
+ num_constants_replaced + 1 + jstate->highest_extern_param_id,
+ jstate->clocations[i].squashed ? " /*, ... */" : "");
+ num_constants_replaced++;
+
+ /* move forward */
+ quer_loc = off + tok_len;
+ last_off = off;
+ last_tok_len = tok_len;
+ }
+
+ /*
+ * We've copied up until the last ignorable constant. Copy over the
+ * remaining bytes of the original query string.
+ */
+ len_to_wrt = query_len - quer_loc;
+
+ Assert(len_to_wrt >= 0);
+ memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
+ n_quer_loc += len_to_wrt;
+
+ Assert(n_quer_loc <= norm_query_buflen);
+ norm_query[n_quer_loc] = '\0';
+
+ *query_len_p = n_quer_loc;
+ return norm_query;
+}
diff --git a/src/include/nodes/queryjumble.h b/src/include/nodes/queryjumble.h
index dcb36dcb44f..cb8741b1d05 100644
--- a/src/include/nodes/queryjumble.h
+++ b/src/include/nodes/queryjumble.h
@@ -91,6 +91,8 @@ extern PGDLLIMPORT int compute_query_id;
extern const char *CleanQuerytext(const char *query, int *location, int *len);
+extern char *GenerateNormalizedQuery(JumbleState *jstate, const char *query,
+ int query_loc, int *query_len_p);
extern JumbleState *JumbleQuery(Query *query);
extern void EnableQueryId(void);
--
2.43.0
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Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Refactor query normalization into core query jumbling
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