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.
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@ -944,11 +944,10 @@ make_union_unique(SetOperationStmt *op, Path *path, List *tlist,
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/*
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* XXX for the moment, take the number of distinct groups as equal to the
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* total input size, ie, the worst case. This is too conservative, but we
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* don't want to risk having the hashtable overrun memory; also, it's not
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* clear how to get a decent estimate of the true size. One should note
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* as well the propensity of novices to write UNION rather than UNION ALL
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* even when they don't expect any duplicates...
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* total input size, ie, the worst case. This is too conservative, but
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* it's not clear how to get a decent estimate of the true size. One
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* should note as well the propensity of novices to write UNION rather
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* than UNION ALL even when they don't expect any duplicates...
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*/
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dNumGroups = path->rows;
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