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Commit3824ca3

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Fix pg_mcv_list deserialization
The memcpy() was copying type OIDs in the wrong direction, so thedeserialized MCV list always had them as 0. This is mostly harmlessexcept when printing the data in pg_mcv_list_items(), in which caseit reported ERROR: cache lookup failed for type 0Also added a simple regression test for pg_mcv_list_items() function,printing a single-item MCV list.Reported-By: Dean RasheedDiscussion:https://postgr.es/m/CAEZATCX6T0iDTTZrqyec4Cd6b4yuL7euu4=rQRXaVBAVrUi1Cg@mail.gmail.com
1 parent4b40e44 commit3824ca3

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3 files changed

+20
-1
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3 files changed

+20
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‎src/backend/statistics/mcv.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -905,7 +905,7 @@ statext_mcv_deserialize(bytea *data)
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VARSIZE_ANY(data),expected_size);
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/* Now copy the array of type Oids. */
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memcpy(ptr,mcvlist->types,sizeof(Oid)*ndims);
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memcpy(mcvlist->types,ptr,sizeof(Oid)*ndims);
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ptr+= (sizeof(Oid)*ndims);
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911911
/* ensure alignment of the pointer (after the header fields) */

‎src/test/regress/expected/stats_ext.out

Lines changed: 11 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -717,6 +717,17 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IS NULL AND
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50 | 50
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(1 row)
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-- test pg_mcv_list_items with a very simple (single item) MCV list
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TRUNCATE mcv_lists;
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INSERT INTO mcv_lists (a, b, c) SELECT 1, 2, 3 FROM generate_series(1,1000) s(i);
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ANALYZE mcv_lists;
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SELECT m.* FROM pg_statistic_ext,
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pg_mcv_list_items(stxmcv) m WHERE stxname = 'mcv_lists_stats';
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index | values | nulls | frequency | base_frequency
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-------+-----------+---------+-----------+----------------
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0 | {1, 2, 3} | {f,f,f} | 1 | 1
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(1 row)
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RESET random_page_cost;
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-- mcv with arrays
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CREATE TABLE mcv_lists_arrays (

‎src/test/regress/sql/stats_ext.sql

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -411,6 +411,14 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IS NULL AND
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SELECT*FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IS NULL AND b IS NULL AND c IS NULL');
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-- test pg_mcv_list_items with a very simple (single item) MCV list
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TRUNCATE mcv_lists;
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INSERT INTO mcv_lists (a, b, c)SELECT1,2,3FROM generate_series(1,1000) s(i);
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ANALYZE mcv_lists;
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SELECT m.*FROM pg_statistic_ext,
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pg_mcv_list_items(stxmcv) mWHERE stxname='mcv_lists_stats';
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RESET random_page_cost;
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-- mcv with arrays

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