Vladimir Sitnikov created CALCITE-3709: ------------------------------------------
Summary: Use "rejected row count" for RelOptCost#getRows Key: CALCITE-3709 URL: https://issues.apache.org/jira/browse/CALCITE-3709 Project: Calcite Issue Type: Improvement Components: core Affects Versions: 1.21.0 Reporter: Vladimir Sitnikov Current cost#rows has a problem: it does not add well when computing cumulative cost. So the idea is to use the number of _rejected_ rows. Then the field would have certain meaning: * If the value is high, the plan is probably rejecting a lot of unrelated rows, thus it is suboptimal * Extra Project/Calc nodes won't artificially increase rows in the cost fields. Currently each Project adds "rows" which is not very good. * It is clear what to put to the rows field: "rejected rows" is more-or-less understandable. For Project it would be 0. * Join/Filter/Calc nodes would show "estimated number of returned rows=X (from metadataquery), rejected rows=Y (from cost)" which would help understanding where the time is spent That is inspired by PostgreSQL's "rows removed by filter" when running explain analyze (which is statement execution + collecting statistics on each execution plan node): http://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.2#Explain_improvements -- This message was sent by Atlassian Jira (v8.3.4#803005)