diff options
| author | Robert Haas | 2015-05-01 12:50:35 +0000 |
|---|---|---|
| committer | Robert Haas | 2015-05-01 12:50:35 +0000 |
| commit | e7cb7ee14555cc9c5773e2c102efd6371f6f2005 (patch) | |
| tree | fc1d7ab49a9f9eee6027a6ace17c37963e514cc9 /src/backend/commands | |
| parent | 2b22795b32576fa7173b501b646581a17de35902 (diff) | |
Allow FDWs and custom scan providers to replace joins with scans.
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.
Diffstat (limited to 'src/backend/commands')
| -rw-r--r-- | src/backend/commands/explain.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index 315a52849c9..f4cc90183a4 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -730,11 +730,17 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used) case T_ValuesScan: case T_CteScan: case T_WorkTableScan: - case T_ForeignScan: - case T_CustomScan: *rels_used = bms_add_member(*rels_used, ((Scan *) plan)->scanrelid); break; + case T_ForeignScan: + *rels_used = bms_add_members(*rels_used, + ((ForeignScan *) plan)->fdw_relids); + break; + case T_CustomScan: + *rels_used = bms_add_members(*rels_used, + ((CustomScan *) plan)->custom_relids); + break; case T_ModifyTable: *rels_used = bms_add_member(*rels_used, ((ModifyTable *) plan)->nominalRelation); @@ -1072,9 +1078,12 @@ ExplainNode(PlanState *planstate, List *ancestors, case T_ValuesScan: case T_CteScan: case T_WorkTableScan: + ExplainScanTarget((Scan *) plan, es); + break; case T_ForeignScan: case T_CustomScan: - ExplainScanTarget((Scan *) plan, es); + if (((Scan *) plan)->scanrelid > 0) + ExplainScanTarget((Scan *) plan, es); break; case T_IndexScan: { |