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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2002-11-19 23:22:00 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2002-11-19 23:22:00 +0000 |
| commit | b60be3f2f8d094da79e04c6eda888f401b09dc39 (patch) | |
| tree | 0590e0647deb5041b8dabcabf03770ebef8e8d43 /doc/src | |
| parent | 54cb1db6cf4d4bf4e44148582bbd2c99684e7dfd (diff) | |
| download | postgresql-b60be3f2f8d094da79e04c6eda888f401b09dc39.tar.gz postgresql-b60be3f2f8d094da79e04c6eda888f401b09dc39.zip | |
Add an at-least-marginally-plausible method of estimating the number
of groups produced by GROUP BY. This improves the accuracy of planning
estimates for grouped subselects, and is needed to check whether a
hashed aggregation plan risks memory overflow.
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