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Fix ANALYZE to accumulate some minimal statistics for an all-null column.

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Per gripes from Mike Mascari and Bernd Heller.
This commit is contained in:
Tom Lane 2005-02-11 00:41:12 +00:00
parent 42599b322d
commit 4db84f0880
1 changed files with 25 additions and 3 deletions
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28
src/backend/commands/analyze.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.81 2005/01/27 23:23:53 neilc Exp $ * $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.82 2005/02/11 00:41:12 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -1548,7 +1548,7 @@ compute_minimal_stats(VacAttrStatsP stats,
} }
} }
/* We can only compute valid stats if we found some non-null values. */ /* We can only compute real stats if we found some non-null values. */
if (nonnull_cnt > 0) if (nonnull_cnt > 0)
{ {
int nmultiple, int nmultiple,
@ -1705,6 +1705,17 @@ compute_minimal_stats(VacAttrStatsP stats,
stats->numvalues[0] = num_mcv; stats->numvalues[0] = num_mcv;
} }
} }
else if (null_cnt > 0)
{
/* We found only nulls; assume the column is entirely null */
stats->stats_valid = true;
stats->stanullfrac = 1.0;
if (is_varwidth)
stats->stawidth = 0; /* "unknown" */
else
stats->stawidth = stats->attrtype->typlen;
stats->stadistinct = 0.0; /* "unknown" */
}
/* We don't need to bother cleaning up any of our temporary palloc's */ /* We don't need to bother cleaning up any of our temporary palloc's */
} }
@ -1812,7 +1823,7 @@ compute_scalar_stats(VacAttrStatsP stats,
values_cnt++; values_cnt++;
} }
/* We can only compute valid stats if we found some sortable values. */ /* We can only compute real stats if we found some sortable values. */
if (values_cnt > 0) if (values_cnt > 0)
{ {
int ndistinct, /* # distinct values in sample */ int ndistinct, /* # distinct values in sample */
@ -2162,6 +2173,17 @@ compute_scalar_stats(VacAttrStatsP stats,
slot_idx++; slot_idx++;
} }
} }
else if (nonnull_cnt == 0 && null_cnt > 0)
{
/* We found only nulls; assume the column is entirely null */
stats->stats_valid = true;
stats->stanullfrac = 1.0;
if (is_varwidth)
stats->stawidth = 0; /* "unknown" */
else
stats->stawidth = stats->attrtype->typlen;
stats->stadistinct = 0.0; /* "unknown" */
}
/* We don't need to bother cleaning up any of our temporary palloc's */ /* We don't need to bother cleaning up any of our temporary palloc's */
} }