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Department of marginal improvements: teach tupconvert.c to avoid doing a

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physical conversion when there are dropped columns in the same places in
the input and output tupdescs.  This avoids possible performance loss from
the recent patch to improve dropped-column handling, in some cases where
the old code would have worked.
This commit is contained in:
Tom Lane
2009-08-17 20:34:31 +00:00
parent 26a90c654f
commit 67a5f8ff9e
1 changed files with 33 additions and 11 deletions
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36
src/backend/access/common/tupconvert.c
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@@ -14,7 +14,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/common/tupconvert.c,v 1.1 2009/08/06 20:44:31 tgl Exp $ * $PostgreSQL: pgsql/src/backend/access/common/tupconvert.c,v 1.2 2009/08/17 20:34:31 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@@ -146,13 +146,24 @@ convert_tuples_by_position(TupleDesc indesc,
{ {
for (i = 0; i < n; i++) for (i = 0; i < n; i++)
{ {
if (attrMap[i] != (i+1)) if (attrMap[i] == (i+1))
{ continue;
/*
* If it's a dropped column and the corresponding input
* column is also dropped, we needn't convert. However,
* attlen and attalign must agree.
*/
if (attrMap[i] == 0 &&
indesc->attrs[i]->attisdropped &&
indesc->attrs[i]->attlen == outdesc->attrs[i]->attlen &&
indesc->attrs[i]->attalign == outdesc->attrs[i]->attalign)
continue;
same = false; same = false;
break; break;
} }
} }
}
else else
same = false; same = false;
@@ -255,13 +266,24 @@ convert_tuples_by_name(TupleDesc indesc,
same = true; same = true;
for (i = 0; i < n; i++) for (i = 0; i < n; i++)
{ {
if (attrMap[i] != (i+1)) if (attrMap[i] == (i+1))
{ continue;
/*
* If it's a dropped column and the corresponding input
* column is also dropped, we needn't convert. However,
* attlen and attalign must agree.
*/
if (attrMap[i] == 0 &&
indesc->attrs[i]->attisdropped &&
indesc->attrs[i]->attlen == outdesc->attrs[i]->attlen &&
indesc->attrs[i]->attalign == outdesc->attrs[i]->attalign)
continue;
same = false; same = false;
break; break;
} }
} }
}
else else
same = false; same = false;