diff options
author | Tom Lane | 2009-08-17 20:34:31 +0000 |
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committer | Tom Lane | 2009-08-17 20:34:31 +0000 |
commit | 3fecffccfdbf8ac692da4e6264e8779962fffc7b (patch) | |
tree | aac71ad4d85f31f5720866f12d5e6ea9704013ed | |
parent | cec33141f6f85ffaf901fe6b7ebbdb50b0b1bc74 (diff) |
Department of marginal improvements: teach tupconvert.c to avoid doing a
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.
-rw-r--r-- | src/backend/access/common/tupconvert.c | 42 |
1 files changed, 32 insertions, 10 deletions
diff --git a/src/backend/access/common/tupconvert.c b/src/backend/access/common/tupconvert.c index b7da973488..5364951992 100644 --- a/src/backend/access/common/tupconvert.c +++ b/src/backend/access/common/tupconvert.c @@ -146,11 +146,22 @@ convert_tuples_by_position(TupleDesc indesc, { for (i = 0; i < n; i++) { - if (attrMap[i] != (i+1)) - { - same = false; - break; - } + 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; + break; } } else @@ -255,11 +266,22 @@ convert_tuples_by_name(TupleDesc indesc, same = true; for (i = 0; i < n; i++) { - if (attrMap[i] != (i+1)) - { - same = false; - break; - } + 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; + break; } } else |