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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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7
src/backend/optimizer/README
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@ -297,9 +297,6 @@ planner()
handle UNION/INTERSECT/EXCEPT, GROUP BY, HAVING, aggregates, handle UNION/INTERSECT/EXCEPT, GROUP BY, HAVING, aggregates,
ORDER BY, DISTINCT, LIMIT ORDER BY, DISTINCT, LIMIT
--query_planner() --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 make list of base relations used in query
split up the qual into restrictions (a=1) and joins (b=c) split up the qual into restrictions (a=1) and joins (b=c)
find qual clauses that enable merge and hash joins 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 Back at standard_join_search(), apply set_cheapest() to extract the
cheapest path for each newly constructed joinrel. cheapest path for each newly constructed joinrel.
Loop back if this wasn't the top join level. 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: Back at grouping_planner:
convert Path tree returned by query_planner into a Plan tree
do grouping(GROUP) do grouping(GROUP)
do aggregates do aggregates
do window functions
make unique(DISTINCT) make unique(DISTINCT)
make sort(ORDER BY) make sort(ORDER BY)
make limit(LIMIT/OFFSET) make limit(LIMIT/OFFSET)