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Disallow extended statistics on system columns

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Since introduction of extended statistics, we've disallowed references
to system columns. So for example

    CREATE STATISTICS s ON ctid FROM t;

would fail. But with extended statistics on expressions, it was possible
to work around this limitation quite easily

    CREATE STATISTICS s ON (ctid::text) FROM t;

This is an oversight in a4d75c86bf, fixed by adding a simple check.
Backpatch to PostgreSQL 14, where support for extended statistics on
expressions was introduced.

Backpatch-through: 14
Discussion: https://postgr.es/m/20210816013255.GS10479%40telsasoft.com
This commit is contained in:
Tomas Vondra 2021-09-20 00:34:57 +02:00
parent d5eeb51bc0
commit c9eeef2a15
1 changed files with 15 additions and 0 deletions
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15
src/backend/commands/statscmds.c
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@ -288,9 +288,24 @@ CreateStatistics(CreateStatsStmt *stmt)
Node *expr = selem->expr;
Oid atttype;
TypeCacheEntry *type;
Bitmapset *attnums = NULL;
int k;
Assert(expr != NULL);
/* Disallow expressions referencing system attributes. */
pull_varattnos(expr, 1, &attnums);
k = -1;
while ((k = bms_next_member(attnums, k)) >= 0)
{
AttrNumber attnum = k + FirstLowInvalidHeapAttributeNumber;
if (attnum <= 0)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("statistics creation on system columns is not supported")));
}
/*
* Disallow data types without a less-than operator.
*