diff options
| author | Simon Riggs <simon@2ndQuadrant.com> | 2015-05-15 14:37:10 -0400 |
|---|---|---|
| committer | Simon Riggs <simon@2ndQuadrant.com> | 2015-05-15 14:37:10 -0400 |
| commit | f6d208d6e51810c73f0e02c477984a6b44627f11 (patch) | |
| tree | 99d540d0b7bda73ff60479f15444f554403d4679 /src/backend/commands/explain.c | |
| parent | 11a83bbedd73800db70f6f2af5a8eb10d15d39d7 (diff) | |
| download | postgresql-f6d208d6e51810c73f0e02c477984a6b44627f11.tar.gz postgresql-f6d208d6e51810c73f0e02c477984a6b44627f11.zip | |
TABLESAMPLE, SQL Standard and extensible
Add a TABLESAMPLE clause to SELECT statements that allows
user to specify random BERNOULLI sampling or block level
SYSTEM sampling. Implementation allows for extensible
sampling functions to be written, using a standard API.
Basic version follows SQLStandard exactly. Usable
concrete use cases for the sampling API follow in later
commits.
Petr Jelinek
Reviewed by Michael Paquier and Simon Riggs
Diffstat (limited to 'src/backend/commands/explain.c')
| -rw-r--r-- | src/backend/commands/explain.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index eeb8f19017e..478771c6ba1 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -731,6 +731,7 @@ ExplainPreScanNode(PlanState *planstate, Bitmapset **rels_used) case T_ValuesScan: case T_CteScan: case T_WorkTableScan: + case T_SampleScan: *rels_used = bms_add_member(*rels_used, ((Scan *) plan)->scanrelid); break; @@ -967,6 +968,21 @@ ExplainNode(PlanState *planstate, List *ancestors, else pname = sname; break; + case T_SampleScan: + { + /* + * Fetch the tablesample method name from RTE. + * + * It would be nice to also show parameters, but since we + * support arbitrary expressions as parameter it might get + * quite messy. + */ + RangeTblEntry *rte; + rte = rt_fetch(((SampleScan *) plan)->scanrelid, es->rtable); + custom_name = get_tablesample_method_name(rte->tablesample->tsmid); + pname = psprintf("Sample Scan (%s)", custom_name); + } + break; case T_Material: pname = sname = "Materialize"; break; @@ -1089,6 +1105,9 @@ ExplainNode(PlanState *planstate, List *ancestors, if (((Scan *) plan)->scanrelid > 0) ExplainScanTarget((Scan *) plan, es); break; + case T_SampleScan: + ExplainScanTarget((Scan *) plan, es); + break; case T_IndexScan: { IndexScan *indexscan = (IndexScan *) plan; @@ -1339,6 +1358,7 @@ ExplainNode(PlanState *planstate, List *ancestors, case T_CteScan: case T_WorkTableScan: case T_SubqueryScan: + case T_SampleScan: show_scan_qual(plan->qual, "Filter", planstate, ancestors, es); if (plan->qual) show_instrumentation_count("Rows Removed by Filter", 1, @@ -2238,6 +2258,7 @@ ExplainTargetRel(Plan *plan, Index rti, ExplainState *es) case T_TidScan: case T_ForeignScan: case T_CustomScan: + case T_SampleScan: case T_ModifyTable: /* Assert it's on a real relation */ Assert(rte->rtekind == RTE_RELATION); |