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Expand partitioned table RTEs level by level, without flattening.

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Flattening the partitioning hierarchy at this stage makes various
desirable optimizations difficult.  The original use case for this
patch was partition-wise join, which wants to match up the partitions
in one partitioning hierarchy with those in another such hierarchy.
However, it now seems that it will also be useful in making partition
pruning work using the PartitionDesc rather than constraint exclusion,
because with a flattened expansion, we have no easy way to figure out
which PartitionDescs apply to which leaf tables in a multi-level
partition hierarchy.

As it turns out, we end up creating both rte->inh and !rte->inh RTEs
for each intermediate partitioned table, just as we previously did for
the root table.  This seems unnecessary since the partitioned tables
have no storage and are not scanned.  We might want to go back and
rejigger things so that no partitioned tables (including the parent)
need !rte->inh RTEs, but that seems to require some adjustments not
related to the core purpose of this patch.

Ashutosh Bapat, reviewed by me and by Amit Langote.  Some final
adjustments by me.

Discussion: http://postgr.es/m/CAFjFpRd=1venqLL7oGU=C1dEkuvk2DJgvF+7uKbnPHaum1mvHQ@mail.gmail.com
This commit is contained in:
Robert Haas
2017-09-14 15:41:08 -04:00
parent 0c4b879b74
commit 0a480502b0
9 changed files with 351 additions and 138 deletions
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8
src/include/nodes/relation.h
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@@ -1935,10 +1935,10 @@ typedef struct SpecialJoinInfo
*
* When we expand an inheritable table or a UNION-ALL subselect into an
* "append relation" (essentially, a list of child RTEs), we build an
* AppendRelInfo for each non-partitioned child RTE. The list of
* AppendRelInfos indicates which child RTEs must be included when expanding
* the parent, and each node carries information needed to translate Vars
* referencing the parent into Vars referencing that child.
* AppendRelInfo for each child RTE. The list of AppendRelInfos indicates
* which child RTEs must be included when expanding the parent, and each node
* carries information needed to translate Vars referencing the parent into
* Vars referencing that child.
*
* These structs are kept in the PlannerInfo node's append_rel_list.
* Note that we just throw all the structs into one list, and scan the