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Commit11be868

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This commit can show EXPLAIN of partial plans including temporary tables.Just for demo. Don't even try to execute that!
1 parent82ed67a commit11be868

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6 files changed

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6 files changed

+370
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‎contrib/Makefile

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@@ -45,6 +45,7 @@ SUBDIRS = \
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spi\
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tablefunc\
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tcn\
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tempscan\
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test_decoding\
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tsm_system_rows\
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tsm_system_time\

‎contrib/tempscan/Makefile

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# contrib/tempscan/Makefile
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MODULE_big = tempscan
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OBJS =\
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$(WIN32RES)\
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nodeCustomTempScan.o\
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EXTENSION = tempscan
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PGFILEDESC = "tempscan - Parallel Scan of Temporary Table"
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REGRESS = basic
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ifdefUSE_PGXS
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PG_CONFIG = pg_config
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PGXS :=$(shell$(PG_CONFIG) --pgxs)
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include$(PGXS)
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else
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subdir = contrib/tempscan
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top_builddir = ../..
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include$(top_builddir)/src/Makefile.global
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include$(top_srcdir)/contrib/contrib-global.mk
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endif

‎contrib/tempscan/expected/basic.out

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--
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-- Copyright (c) 2017-2024, Postgres Professional
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--
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-- Set of basic regression tests on scanning of a temporary table in parallel
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--
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-- Load the library. It should be load dynamically
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LOAD 'tempscan';
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-- Force usage of parallel workers
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SET max_parallel_workers_per_gather = 3;
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SET parallel_setup_cost = 0.0001;
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SET parallel_tuple_cost = 0.0001;
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-- Don't need big tables
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SET min_parallel_table_scan_size = 0;
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SET min_parallel_index_scan_size = 0;
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CREATE TABLE parallel_test (x int);
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INSERT INTO parallel_test (x) SELECT x FROM generate_series(1,100) AS x;
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CREATE TEMP TABLE parallel_test_tmp AS (SELECT * FROM parallel_test);
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VACUUM ANALYZE parallel_test, parallel_test_tmp;
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SET tempscan.enable = 'on';
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EXPLAIN (COSTS OFF)
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SELECT count(*) FROM parallel_test;
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QUERY PLAN
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------------------------------------------------------
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Finalize Aggregate
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-> Gather
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Workers Planned: 1
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-> Partial Aggregate
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-> Parallel Seq Scan on parallel_test
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(5 rows)
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-- Should also utilise parallel workers like scanning of a plain table
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EXPLAIN (COSTS OFF)
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SELECT count(*) FROM parallel_test_tmp;
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QUERY PLAN
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----------------------------------------------------------
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Aggregate
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-> Gather
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Workers Planned: 1
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-> Custom Scan (nodeCustomTempScan)
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-> Parallel Seq Scan on parallel_test_tmp
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(5 rows)
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RESET tempscan.enable;
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DROP TABLE parallel_test, parallel_test_tmp;

‎contrib/tempscan/nodeCustomTempScan.c

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/* -------------------------------------------------------------------------
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*
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* nodeCustomTempScan.c
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*Implements strategy which allows to build and execute partial paths for
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*a query which contains tempoorary table scans.
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*
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* Copyright (c) 2017-2024, Postgres Professional
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*
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* IDENTIFICATION
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*contrib/tempscan/nodeCustomTempScan.c
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*
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* -------------------------------------------------------------------------
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*/
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#include"postgres.h"
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#include"nodes/extensible.h"
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#include"optimizer/cost.h"
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#include"optimizer/pathnode.h"
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#include"optimizer/paths.h"
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#include"utils/guc.h"
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#include"utils/lsyscache.h"
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#include"utils/rel.h"
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PG_MODULE_MAGIC;
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#defineMODULENAME"tempscan"
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#defineNODENAME"nodeCustomTempScan"
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staticPlan*create_partial_tempscan_plan(PlannerInfo*root,
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RelOptInfo*rel,
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CustomPath*best_path,
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List*tlist,
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List*scan_clauses,
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List*custom_plans);
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staticNode*create_tempscan_state(CustomScan*cscan);
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staticvoidBeginTempScan(CustomScanState*node,EState*estate,inteflags);
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staticTupleTableSlot*ExecTempScan(CustomScanState*node);
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staticvoidEndTempScan(CustomScanState*node);
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staticvoidReScanTempScan(CustomScanState*node);
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staticCustomPathMethodspath_methods=
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{
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.CustomName=NODENAME,
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.PlanCustomPath=create_partial_tempscan_plan,
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.ReparameterizeCustomPathByChild=NULL
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};
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staticCustomScanMethodsplan_methods=
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{
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.CustomName=NODENAME,
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.CreateCustomScanState=create_tempscan_state
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};
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staticCustomExecMethodsexec_methods=
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{
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.CustomName=NODENAME,
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.BeginCustomScan=BeginTempScan,
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.ExecCustomScan=ExecTempScan,
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.EndCustomScan=EndTempScan,
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.ReScanCustomScan=ReScanTempScan,
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.MarkPosCustomScan=NULL,
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.RestrPosCustomScan=NULL,
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.EstimateDSMCustomScan=NULL,
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.InitializeDSMCustomScan=NULL,
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.ReInitializeDSMCustomScan=NULL,
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.InitializeWorkerCustomScan=NULL,
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.ShutdownCustomScan=NULL,
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.ExplainCustomScan=NULL
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};
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staticset_rel_pathlist_hook_typeset_rel_pathlist_hook_next=NULL;
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staticbooltempscan_enable= false;
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void_PG_init(void);
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/*
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* The input path shouldn't be a part of the relation pathlist.
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*/
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staticCustomPath*
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create_partial_tempscan_path(PlannerInfo*root,RelOptInfo*rel,
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Path*path)
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{
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CustomPath*cpath;
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Path*pathnode;
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cpath=makeNode(CustomPath);
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pathnode=&cpath->path;
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pathnode->pathtype=T_CustomScan;
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pathnode->parent=rel;
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pathnode->pathtarget=rel->reltarget;
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pathnode->rows=rel->rows;
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/* XXX: Just for now */
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pathnode->param_info=NULL;
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pathnode->parallel_safe= true;
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pathnode->parallel_aware= false;
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pathnode->parallel_workers=path->parallel_workers;
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/* DEBUGGING purposes only */
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pathnode->startup_cost=path->startup_cost /disable_cost;
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pathnode->total_cost=path->total_cost /disable_cost;
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cpath->custom_paths=list_make1(path);
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cpath->custom_private=NIL;
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cpath->custom_restrictinfo=NIL;
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cpath->methods=&path_methods;
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returncpath;
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}
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staticPlan*
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create_partial_tempscan_plan(PlannerInfo*root,RelOptInfo*rel,
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CustomPath*best_path,List*tlist,
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List*scan_clauses,List*custom_plans)
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{
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CustomScan*cscan=makeNode(CustomScan);
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Assert(list_length(custom_plans)==1);
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Assert(best_path->path.parallel_safe= true&&
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best_path->path.parallel_workers>0);
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cscan->scan.plan.targetlist=cscan->custom_scan_tlist=tlist;
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cscan->scan.scanrelid=0;
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cscan->custom_exprs=NIL;
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cscan->custom_plans=custom_plans;
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cscan->methods=&plan_methods;
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cscan->flags=best_path->flags;
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cscan->custom_private=best_path->custom_private;
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return&cscan->scan.plan;
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}
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staticNode*
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create_tempscan_state(CustomScan*cscan)
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{
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CustomScanState*cstate=makeNode(CustomScanState);
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cstate->methods=&exec_methods;
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return (Node*)cstate;
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}
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staticvoid
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BeginTempScan(CustomScanState*node,EState*estate,inteflags)
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{
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CustomScan*cscan= (CustomScan*)node->ss.ps.plan;
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Plan*subplan;
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PlanState*pstate;
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Assert(list_length(cscan->custom_plans)==1);
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subplan= (Plan*)linitial(cscan->custom_plans);
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pstate=ExecInitNode(subplan,estate,eflags);
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node->custom_ps=lappend(node->custom_ps, (void*)pstate);
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}
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staticTupleTableSlot*
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ExecTempScan(CustomScanState*node)
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{
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Assert(list_length(node->custom_ps)==1);
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returnExecProcNode((PlanState*)linitial(node->custom_ps));
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}
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staticvoid
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EndTempScan(CustomScanState*node)
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{
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ExecClearTuple(node->ss.ss_ScanTupleSlot);
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ExecEndNode((PlanState*)linitial(node->custom_ps));
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}
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staticvoid
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ReScanTempScan(CustomScanState*node)
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{
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PlanState*child;
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ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
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child= (PlanState*)linitial(node->custom_ps);
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if (node->ss.ps.chgParam!=NULL)
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UpdateChangedParamSet(child,node->ss.ps.chgParam);
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ExecReScan(child);
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}
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/*
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* Try to add partial paths to the scan of a temporary table.
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*
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* In contrast to the hook on a JOIN paths creation, here we already at the end
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* of paths creation procedure, right before insertion of a gather node.
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* So, we can discover pathlist and choose any base path we can and want to use
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* in parallel scan.
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*
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* TODO: add inner strategy for temp table scan (parallel_workers == 0,
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* parallel_safe == true). Right now it looks a bit more difficult to implement.
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*/
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staticvoid
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try_partial_tempscan(PlannerInfo*root,RelOptInfo*rel,Indexrti,
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RangeTblEntry*rte)
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{
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intparallel_workers;
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Path*path;
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/*
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* Some extension intercept this hook earlier. Allow it to do a work
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* before us.
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*/
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if (set_rel_pathlist_hook_next)
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(*set_rel_pathlist_hook_next)(root,rel,rti,rte);
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if (rel->consider_parallel)
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return;
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if (rte->rtekind!=RTE_RELATION||
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get_rel_persistence(rte->relid)!=RELPERSISTENCE_TEMP)
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return;
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parallel_workers=compute_parallel_worker(rel,rel->pages,-1,
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max_parallel_workers_per_gather);
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/* If any limit was set to zero, the user doesn't want a parallel scan. */
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if (parallel_workers <=0)
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return;
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/* HACK */
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rel->consider_parallel= true;
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path=create_seqscan_path(root,rel,NULL,parallel_workers);
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if (path)
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{
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/* Add an unordered partial path based on a parallel sequential scan. */
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add_partial_path(rel, (Path*)
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create_partial_tempscan_path(root,rel,path));
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}
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if (!bms_equal(rel->relids,root->all_query_rels))
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rel->consider_parallel= false;
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Assert(IsA(linitial(rel->partial_pathlist),CustomPath));
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}
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void
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_PG_init(void)
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{
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DefineCustomBoolVariable("tempscan.enable",
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"Enable feature of the parallel temporary table scan.",
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"Right now no any other purpose except debugging",
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&tempscan_enable,
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false,
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PGC_SUSET,
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0,
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NULL,
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NULL,
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NULL
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);
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set_rel_pathlist_hook_next=set_rel_pathlist_hook;
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set_rel_pathlist_hook=try_partial_tempscan;
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MarkGUCPrefixReserved(MODULENAME);
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}

‎contrib/tempscan/sql/basic.sql

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--
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-- Copyright (c) 2017-2024, Postgres Professional
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--
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-- Set of basic regression tests on scanning of a temporary table in parallel
5+
--
6+
7+
-- Load the library. It should be load dynamically
8+
LOAD'tempscan';
9+
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-- Force usage of parallel workers
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SET max_parallel_workers_per_gather=3;
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SET parallel_setup_cost=0.0001;
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SET parallel_tuple_cost=0.0001;
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-- Don't need big tables
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SET min_parallel_table_scan_size=0;
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SET min_parallel_index_scan_size=0;
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CREATETABLEparallel_test (xint);
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INSERT INTO parallel_test (x)SELECT xFROM generate_series(1,100)AS x;
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CREATE TEMP TABLE parallel_test_tmpAS (SELECT*FROM parallel_test);
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VACUUM ANALYZE parallel_test, parallel_test_tmp;
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SETtempscan.enable='on';
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EXPLAIN (COSTS OFF)
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SELECTcount(*)FROM parallel_test;
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-- Should also utilise parallel workers like scanning of a plain table
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EXPLAIN (COSTS OFF)
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SELECTcount(*)FROM parallel_test_tmp;
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RESETtempscan.enable;
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DROPTABLE parallel_test, parallel_test_tmp;

‎contrib/tempscan/tempscan.control

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# tempscan
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comment = 'Parallel Temp Table Scan'
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default_version = '0.1'
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module_pathname = '$libdir/tempscan'
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relocatable = true

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