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Commit3c03b8c

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pg_stat_statements: Fix parameter number gaps in normalized queries
pg_stat_statements anticipates that certain constant locations may berecorded multiple times and attempts to avoid calculating a length forthese locations in fill_in_constant_lengths().However, during generate_normalized_query() where normalized querystrings are generated, these locations are not excluded fromconsideration. This could increment the parameter number counter forevery recorded occurrence at such a location, leading to an incorrectnormalization in certain cases with gaps in the numbers reported.For example, take this query:SELECT WHERE '1' IN ('2'::int, '3'::int::text)Before this commit, it would be normalized like that, with gaps in theparameter numbers:SELECT WHERE $1 IN ($3::int, $4::int::text)However the correct, less confusing one should be like that:SELECT WHERE $1 IN ($2::int, $3::int::text)This commit fixes the computation of the parameter numbers to track thenumber of constants replaced with an $n by a separate counter instead ofthe iterator used to loop through the list of locations.The underlying query IDs are not changed, neither are the normalizedstrings for existing PGSS hash entries. New entries with freshnormalized queries would automatically get reshaped based on the newparameter numbering.Issue discovered while discussing a separate problem for HEAD, but thisaffects all the stable branches.Author: Sami Imseih <samimseih@gmail.com>Discussion:https://postgr.es/m/CAA5RZ0tzxvWXsacGyxrixdhy3tTTDfJQqxyFBRFh31nNHBQ5qA@mail.gmail.comBackpatch-through: 13
1 parent31ee5ec commit3c03b8c

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3 files changed

+40
-1
lines changed

3 files changed

+40
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‎contrib/pg_stat_statements/expected/pg_stat_statements.out

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@@ -398,6 +398,35 @@ SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
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SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C" | 0 | 0
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(6 rows)
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-- normalization of constants and parameters, with constant locations
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-- recorded one or more times.
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SELECT pg_stat_statements_reset() IS NOT NULL AS t;
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t
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---
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t
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(1 row)
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SELECT WHERE '1' IN ('1'::int, '3'::int::text);
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--
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(1 row)
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SELECT WHERE (1, 2) IN ((1, 2), (2, 3));
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--
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(1 row)
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SELECT WHERE (3, 4) IN ((5, 6), (8, 7));
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--
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(0 rows)
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SELECT query, calls FROM pg_stat_statements ORDER BY query COLLATE "C";
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query | calls
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------------------------------------------------------------------------+-------
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SELECT WHERE $1 IN ($2::int, $3::int::text) | 1
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SELECT WHERE ($1, $2) IN (($3, $4), ($5, $6)) | 2
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SELECT pg_stat_statements_reset() IS NOT NULL AS t | 1
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SELECT query, calls FROM pg_stat_statements ORDER BY query COLLATE "C" | 0
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(4 rows)
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--
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-- queries with locking clauses
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--

‎contrib/pg_stat_statements/pg_stat_statements.c

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Original file line numberDiff line numberDiff line change
@@ -3278,6 +3278,7 @@ generate_normalized_query(pgssJumbleState *jstate, const char *query,
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n_quer_loc=0,/* Normalized query byte location */
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last_off=0,/* Offset from start for previous tok */
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last_tok_len=0;/* Length (in bytes) of that tok */
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intnum_constants_replaced=0;
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/*
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* Get constants' lengths (core system only gives us locations). Note
@@ -3321,7 +3322,8 @@ generate_normalized_query(pgssJumbleState *jstate, const char *query,
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/* And insert a param symbol in place of the constant token */
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n_quer_loc+=sprintf(norm_query+n_quer_loc,"$%d",
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i+1+jstate->highest_extern_param_id);
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num_constants_replaced+1+jstate->highest_extern_param_id);
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num_constants_replaced++;
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quer_loc=off+tok_len;
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last_off=off;

‎contrib/pg_stat_statements/sql/pg_stat_statements.sql

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@@ -201,6 +201,14 @@ SELECT PLUS_ONE(1);
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SELECT query, calls, rowsFROM pg_stat_statementsORDER BY query COLLATE"C";
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-- normalization of constants and parameters, with constant locations
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-- recorded one or more times.
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SELECT pg_stat_statements_reset()IS NOT NULLAS t;
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SELECTWHERE'1'IN ('1'::int,'3'::int::text);
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SELECTWHERE (1,2)IN ((1,2), (2,3));
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SELECTWHERE (3,4)IN ((5,6), (8,7));
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SELECT query, callsFROM pg_stat_statementsORDER BY query COLLATE"C";
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--
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-- queries with locking clauses
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--

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