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postgres_fdw: Refactor deparsing code for locking clauses. 

The upcoming patch to allow join pushdown in postgres_fdw needs to use
this code multiple times, which requires moving it to deparse.c.  That
seems like a good idea anyway, so do that now both on general principle
and to simplify the future patch.

Inspired by a patch by Shigeru Hanada and Ashutosh Bapat, but I did
it a little differently than what that patch did.
This commit is contained in:
Robert Haas 2016-01-28 16:44:01 -05:00
parent fbe5a3fb73
commit b88ef201d4
3 changed files with 64 additions and 49 deletions
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60
contrib/postgres_fdw/deparse.c
View File

@ -45,7 +45,9 @@
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "nodes/nodeFuncs.h"
#include "nodes/plannodes.h"
#include "optimizer/clauses.h"
#include "optimizer/prep.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
@ -807,6 +809,64 @@ deparseTargetList(StringInfo buf,
appendStringInfoString(buf, "NULL");
}
/*
* Deparse the appropriate locking clause (FOR SELECT or FOR SHARE) for a
* given relation.
*/
void
deparseLockingClause(StringInfo buf, PlannerInfo *root, RelOptInfo *rel)
{
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local tables.
* The extra roundtrips involved in trying to duplicate the local
* semantics exactly don't seem worthwhile (see also comments for
* RowMarkType).
*
* Note: because we actually run the query as a cursor, this assumes that
* DECLARE CURSOR ... FOR UPDATE is supported, which it isn't before 8.3.
*/
if (rel->relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
appendStringInfoString(buf, " FOR UPDATE");
}
else
{
PlanRowMark *rc = get_plan_rowmark(root->rowMarks, rel->relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so handle
* that. (But we could also see LCS_NONE, meaning this isn't a
* target relation after all.)
*
* For now, just ignore any [NO] KEY specification, since (a) it's
* not clear what that means for a remote table that we don't have
* complete information about, and (b) it wouldn't work anyway on
* older remote servers. Likewise, we don't worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_NONE:
/* No locking needed */
break;
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
appendStringInfoString(buf, " FOR SHARE");
break;
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
appendStringInfoString(buf, " FOR UPDATE");
break;
}
}
}
}
/*
* Deparse WHERE clauses in given list of RestrictInfos and append them to buf.
*

51
contrib/postgres_fdw/postgres_fdw.c
View File

@ -1013,55 +1013,8 @@ postgresGetForeignPlan(PlannerInfo *root,
if (best_path->path.pathkeys)
appendOrderByClause(&sql, root, baserel, best_path->path.pathkeys);
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local tables.
* The extra roundtrips involved in trying to duplicate the local
* semantics exactly don't seem worthwhile (see also comments for
* RowMarkType).
*
* Note: because we actually run the query as a cursor, this assumes that
* DECLARE CURSOR ... FOR UPDATE is supported, which it isn't before 8.3.
*/
if (baserel->relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
appendStringInfoString(&sql, " FOR UPDATE");
}
else
{
PlanRowMark *rc = get_plan_rowmark(root->rowMarks, baserel->relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so handle
* that. (But we could also see LCS_NONE, meaning this isn't a
* target relation after all.)
*
* For now, just ignore any [NO] KEY specification, since (a) it's
* not clear what that means for a remote table that we don't have
* complete information about, and (b) it wouldn't work anyway on
* older remote servers. Likewise, we don't worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_NONE:
/* No locking needed */
break;
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
appendStringInfoString(&sql, " FOR SHARE");
break;
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
appendStringInfoString(&sql, " FOR UPDATE");
break;
}
}
}
/* Add any necessary FOR UPDATE/SHARE. */
deparseLockingClause(&sql, root, baserel);
/*
* Build the fdw_private list that will be available to the executor.

2
contrib/postgres_fdw/postgres_fdw.h
View File

@ -88,6 +88,8 @@ extern void deparseSelectSql(StringInfo buf,
RelOptInfo *baserel,
Bitmapset *attrs_used,
List **retrieved_attrs);
extern void deparseLockingClause(StringInfo buf,
PlannerInfo *root, RelOptInfo *rel);
extern void appendWhereClause(StringInfo buf,
PlannerInfo *root,
RelOptInfo *baserel,