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authorTom Lane <tgl@sss.pgh.pa.us>2005-01-28 20:35:14 +0000
committerTom Lane <tgl@sss.pgh.pa.us>2005-01-28 20:35:14 +0000
commit7c67dcacd83c885618a58936df627a17470d9991 (patch)
tree759f3d24900f14b55cd260b5ef8bddc8fa22df2b /doc/src/sgml/ref/postgres-ref.sgml
parenta098f533d15efe5552c0b6cd661cc123231c8c54 (diff)
When dealing with multiple grouping columns coming from the same table,
clamp the estimated number of groups to table row count over 10, instead of table row count; this reflects a heuristic that people probably won't group over a near-unique set of columns, and the knowledge that we don't currently have any way to estimate the correlation of the columns better than guessing. This change creates a trivial plan change in one of the regression tests.
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