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Simplify handling of remote-qual pass-forward in postgres_fdw.

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Commit 0bf3ae88a encountered a need to pass the finally chosen remote qual
conditions forward from postgresGetForeignPlan to postgresPlanDirectModify.
It solved that by sticking them into the plan node's fdw_private list,
which in hindsight was a pretty bad idea.  In the first place, there's no
use for those qual trees either in EXPLAIN or execution; indeed they could
never safely be used for any post-planning purposes, because they would not
get processed by setrefs.c.  So they're just dead weight to carry around in
the finished plan tree, plus being an attractive nuisance for somebody who
might get the idea that they could be used that way.  Secondly, because
those qual trees (sometimes) contained RestrictInfos, they created a
plan-transmission hazard for parallel query, which is how come we noticed a
problem.  We dealt with that symptom in commit 28b047875, but really a more
straightforward and more efficient fix is to pass the data through in a new
field of struct PgFdwRelationInfo.  So do it that way.  (There's no need
to revert 28b047875, as it has sufficient reason to live anyway.)

Per fuzz testing by Andreas Seltenreich.

Discussion: https://postgr.es/m/87tw5x4vcu.fsf@credativ.de
This commit is contained in:
Tom Lane
2017-04-11 13:53:13 -04:00
parent 02af7857e5
commit 88e902b769
2 changed files with 29 additions and 24 deletions
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9
contrib/postgres_fdw/postgres_fdw.h
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@ -22,7 +22,10 @@
/*
* FDW-specific planner information kept in RelOptInfo.fdw_private for a
* foreign table. This information is collected by postgresGetForeignRelSize.
* postgres_fdw foreign table. For a baserel, this struct is created by
* postgresGetForeignRelSize, although some fields are not filled till later.
* postgresGetForeignJoinPaths creates it for a joinrel, and
* postgresGetForeignUpperPaths creates it for an upperrel.
*/
typedef struct PgFdwRelationInfo
{
@ -40,6 +43,9 @@ typedef struct PgFdwRelationInfo
List *remote_conds;
List *local_conds;
/* Actual remote restriction clauses for scan (sans RestrictInfos) */
List *final_remote_exprs;
/* Bitmap of attr numbers we need to fetch from the remote server. */
Bitmapset *attrs_used;
@ -83,6 +89,7 @@ typedef struct PgFdwRelationInfo
RelOptInfo *outerrel;
RelOptInfo *innerrel;
JoinType jointype;
/* joinclauses contains only JOIN/ON conditions for an outer join */
List *joinclauses; /* List of RestrictInfo */
/* Grouping information */