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Allow FDWs and custom scan providers to replace joins with scans.

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Foreign data wrappers can use this capability for so-called "join
pushdown"; that is, instead of executing two separate foreign scans
and then joining the results locally, they can generate a path which
performs the join on the remote server and then is scanned locally.
This commit does not extend postgres_fdw to take advantage of this
capability; it just provides the infrastructure.

Custom scan providers can use this in a similar way.  Previously,
it was only possible for a custom scan provider to scan a single
relation.  Now, it can scan an entire join tree, provided of course
that it knows how to produce the same results that the join would
have produced if executed normally.

KaiGai Kohei, reviewed by Shigeru Hanada, Ashutosh Bapat, and me.
This commit is contained in:
Robert Haas
2015-05-01 08:50:35 -04:00
parent 2b22795b32
commit e7cb7ee145
20 changed files with 448 additions and 71 deletions
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145
src/backend/optimizer/plan/setrefs.c
View File

@ -86,6 +86,12 @@ static void flatten_unplanned_rtes(PlannerGlobal *glob, RangeTblEntry *rte);
static bool flatten_rtes_walker(Node *node, PlannerGlobal *glob);
static void add_rte_to_flat_rtable(PlannerGlobal *glob, RangeTblEntry *rte);
static Plan *set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset);
static void set_foreignscan_references(PlannerInfo *root,
ForeignScan *fscan,
int rtoffset);
static void set_customscan_references(PlannerInfo *root,
CustomScan *cscan,
int rtoffset);
static Plan *set_indexonlyscan_references(PlannerInfo *root,
IndexOnlyScan *plan,
int rtoffset);
@ -565,31 +571,11 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
}
break;
case T_ForeignScan:
{
ForeignScan *splan = (ForeignScan *) plan;
splan->scan.scanrelid += rtoffset;
splan->scan.plan.targetlist =
fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
splan->scan.plan.qual =
fix_scan_list(root, splan->scan.plan.qual, rtoffset);
splan->fdw_exprs =
fix_scan_list(root, splan->fdw_exprs, rtoffset);
}
set_foreignscan_references(root, (ForeignScan *) plan, rtoffset);
break;
case T_CustomScan:
{
CustomScan *splan = (CustomScan *) plan;
splan->scan.scanrelid += rtoffset;
splan->scan.plan.targetlist =
fix_scan_list(root, splan->scan.plan.targetlist, rtoffset);
splan->scan.plan.qual =
fix_scan_list(root, splan->scan.plan.qual, rtoffset);
splan->custom_exprs =
fix_scan_list(root, splan->custom_exprs, rtoffset);
}
set_customscan_references(root, (CustomScan *) plan, rtoffset);
break;
case T_NestLoop:
@ -876,6 +862,121 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
return plan;
}
/*
* set_foreignscan_references
* Do set_plan_references processing on an ForeignScan
*/
static void
set_foreignscan_references(PlannerInfo *root,
ForeignScan *fscan,
int rtoffset)
{
if (rtoffset > 0)
{
Bitmapset *tempset = NULL;
int x = -1;
while ((x = bms_next_member(fscan->fdw_relids, x)) >= 0)
tempset = bms_add_member(tempset, x + rtoffset);
fscan->fdw_relids = tempset;
}
if (fscan->scan.scanrelid == 0)
{
indexed_tlist *pscan_itlist = build_tlist_index(fscan->fdw_ps_tlist);
fscan->scan.plan.targetlist = (List *)
fix_upper_expr(root,
(Node *) fscan->scan.plan.targetlist,
pscan_itlist,
INDEX_VAR,
rtoffset);
fscan->scan.plan.qual = (List *)
fix_upper_expr(root,
(Node *) fscan->scan.plan.qual,
pscan_itlist,
INDEX_VAR,
rtoffset);
fscan->fdw_exprs = (List *)
fix_upper_expr(root,
(Node *) fscan->fdw_exprs,
pscan_itlist,
INDEX_VAR,
rtoffset);
fscan->fdw_ps_tlist =
fix_scan_list(root, fscan->fdw_ps_tlist, rtoffset);
pfree(pscan_itlist);
}
else
{
fscan->scan.scanrelid += rtoffset;
fscan->scan.plan.targetlist =
fix_scan_list(root, fscan->scan.plan.targetlist, rtoffset);
fscan->scan.plan.qual =
fix_scan_list(root, fscan->scan.plan.qual, rtoffset);
fscan->fdw_exprs =
fix_scan_list(root, fscan->fdw_exprs, rtoffset);
}
}
/*
* set_customscan_references
* Do set_plan_references processing on an CustomScan
*/
static void
set_customscan_references(PlannerInfo *root,
CustomScan *cscan,
int rtoffset)
{
if (rtoffset > 0)
{
Bitmapset *tempset = NULL;
int x = -1;
while ((x = bms_next_member(cscan->custom_relids, x)) >= 0)
tempset = bms_add_member(tempset, x + rtoffset);
cscan->custom_relids = tempset;
}
if (cscan->scan.scanrelid == 0)
{
indexed_tlist *pscan_itlist =
build_tlist_index(cscan->custom_ps_tlist);
cscan->scan.plan.targetlist = (List *)
fix_upper_expr(root,
(Node *) cscan->scan.plan.targetlist,
pscan_itlist,
INDEX_VAR,
rtoffset);
cscan->scan.plan.qual = (List *)
fix_upper_expr(root,
(Node *) cscan->scan.plan.qual,
pscan_itlist,
INDEX_VAR,
rtoffset);
cscan->custom_exprs = (List *)
fix_upper_expr(root,
(Node *) cscan->custom_exprs,
pscan_itlist,
INDEX_VAR,
rtoffset);
cscan->custom_ps_tlist =
fix_scan_list(root, cscan->custom_ps_tlist, rtoffset);
pfree(pscan_itlist);
}
else
{
cscan->scan.scanrelid += rtoffset;
cscan->scan.plan.targetlist =
fix_scan_list(root, cscan->scan.plan.targetlist, rtoffset);
cscan->scan.plan.qual =
fix_scan_list(root, cscan->scan.plan.qual, rtoffset);
cscan->custom_exprs =
fix_scan_list(root, cscan->custom_exprs, rtoffset);
}
}
/*
* set_indexonlyscan_references
* Do set_plan_references processing on an IndexOnlyScan