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Fix some obsolete information in src/backend/optimizer/README.

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Constant quals aren't handled the same way they used to be.  Also,
add mention of a couple more major steps in grouping_planner.
Per complaint a couple months back from Etsuro Fujita.
This commit is contained in:
Tom Lane 2013-11-05 11:31:35 -05:00
parent 732758db4c
commit 6331de1d44
1 changed files with 2 additions and 5 deletions
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src/backend/optimizer/README
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@ -297,9 +297,6 @@ planner()
handle UNION/INTERSECT/EXCEPT, GROUP BY, HAVING, aggregates,
ORDER BY, DISTINCT, LIMIT
--query_planner()
pull out constant quals, which can be used to gate execution of the
whole plan (if any are found, we make a top-level Result node
to do the gating)
make list of base relations used in query
split up the qual into restrictions (a=1) and joins (b=c)
find qual clauses that enable merge and hash joins
@ -318,11 +315,11 @@ planner()
Back at standard_join_search(), apply set_cheapest() to extract the
cheapest path for each newly constructed joinrel.
Loop back if this wasn't the top join level.
Back at query_planner:
put back any constant quals by adding a Result node
Back at grouping_planner:
convert Path tree returned by query_planner into a Plan tree
do grouping(GROUP)
do aggregates
do window functions
make unique(DISTINCT)
make sort(ORDER BY)
make limit(LIMIT/OFFSET)