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| author | Peter Geoghegan <pg@bowt.ie> | 2020-07-28 17:14:07 -0700 |
|---|---|---|
| committer | Peter Geoghegan <pg@bowt.ie> | 2020-07-28 17:14:07 -0700 |
| commit | b1d79127ed875f04720d2c4677a75f43528bfe08 (patch) | |
| tree | 1cd3db277317cd7e00c965f7db38e288577af609 /src | |
| parent | f36e82072c8866ba2eca08d88d1a5c3e0c3d1eb4 (diff) | |
| download | postgresql-b1d79127ed875f04720d2c4677a75f43528bfe08.tar.gz postgresql-b1d79127ed875f04720d2c4677a75f43528bfe08.zip | |
Correct obsolete UNION hash aggs comment.
Oversight in commit 1f39bce0, which added disk-based hash aggregation.
Backpatch: 13-, where disk-based hash aggregation was introduced.
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/prep/prepunion.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c index 951aed80e7a..6588f83d5ec 100644 --- a/src/backend/optimizer/prep/prepunion.c +++ b/src/backend/optimizer/prep/prepunion.c @@ -944,11 +944,10 @@ make_union_unique(SetOperationStmt *op, Path *path, List *tlist, /* * XXX for the moment, take the number of distinct groups as equal to the - * total input size, ie, the worst case. This is too conservative, but we - * don't want to risk having the hashtable overrun memory; also, it's not - * clear how to get a decent estimate of the true size. One should note - * as well the propensity of novices to write UNION rather than UNION ALL - * even when they don't expect any duplicates... + * total input size, ie, the worst case. This is too conservative, but + * it's not clear how to get a decent estimate of the true size. One + * should note as well the propensity of novices to write UNION rather + * than UNION ALL even when they don't expect any duplicates... */ dNumGroups = path->rows; |