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Re-enable error for "SELECT ... OFFSET -1".

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The executor has thrown errors for negative OFFSET values since 8.4 (see
commit bfce56eea4), but in a moment of brain
fade I taught the planner that OFFSET with a constant negative value was a
no-op (commit 1a1832eb08).  Reinstate the
former behavior by only discarding OFFSET with a value of exactly 0.  In
passing, adjust a planner comment that referenced the ancient behavior.

Back-patch to 9.3 where the mistake was introduced.
This commit is contained in:
Tom Lane 2014-07-22 13:30:01 -04:00
parent f59c8eff7d
commit 6306d07122
1 changed files with 3 additions and 4 deletions
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7
src/backend/optimizer/plan/planner.c
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@ -2127,7 +2127,7 @@ preprocess_limit(PlannerInfo *root, double tuple_fraction,
{
*offset_est = DatumGetInt64(((Const *) est)->constvalue);
if (*offset_est < 0)
*offset_est = 0; /* less than 0 is same as 0 */
*offset_est = 0; /* treat as not present */
}
}
else
@ -2288,9 +2288,8 @@ limit_needed(Query *parse)
{
int64 offset = DatumGetInt64(((Const *) node)->constvalue);
/* Executor would treat less-than-zero same as zero */
if (offset > 0)
return true; /* OFFSET with a positive value */
if (offset != 0)
return true; /* OFFSET with a nonzero value */
}
}
else