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Correct obsolete UNION hash aggs comment.
2020年7月29日 00:14:07 +0000 (17:14 -0700)
2020年7月29日 00:14:07 +0000 (17:14 -0700)
Oversight in commit 1f39bce0, which added disk-based hash aggregation.

Backpatch: 13-, where disk-based hash aggregation was introduced.


diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c
index 951aed80e7a20df8991bb50f0a33898b971d2712..6588f83d5ec6fde6491db599b12565ac736ec8bc 100644 (file)
--- 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;
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