Explicit Redistribute Motion
The Explicit Redistribute iterator moves tuples to segments explicitly specified in the segment ID column of the tuples. This is differs from a Redistribute Motion iterator, where target segments are indirectly specified through hash expressions.
testdb=# explain delete from t1 where t1.id in (select id from t2); QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------- Delete (slice0; segments: 6) (rows=4279005 width=10) -> Explicit Redistribute Motion 6:6 (slice3; segments: 6) (cost=57114.23..338731.20 rows=4279005 width=10) -> Hash Join (cost=57114.23..338731.20 rows=4279005 width=10) Hash Cond: t1.id = t2.id -> Append-only Scan on t1 (cost=0.00..16880.00 rows=266667 width=14) -> Hash (cost=55868.87..55868.87 rows=16605 width=4) -> Broadcast Motion 6:6 (slice2; segments: 6) (cost=52880.00..55868.87 rows=16605 width=4) -> HashAggregate (cost=52880.00..53876.29 rows=16605 width=4) Group By: t2.id -> Redistribute Motion 6:6 (slice1; segments: 6) (cost=0.00..48880.00 rows=266667 width=4) Hash Key: t2.id -> Append-only Scan on t2 (cost=0.00..16880.00 rows=266667 width=4) Optimizer status: legacy query optimizer (13 rows)
1. 做plan时，调用preprocess_targetlist， 对update，delete，target list中加入 ctid和segment id；
(gdb) bt #0 preprocess_targetlist (root=0x2304f58, tlist=0x0) at preptlist.c:152 #1 0x00000000007e868c in grouping_planner (root=0x2304f58, tuple_fraction=0) at planner.c:1814 #2 0x00000000007e79d7 in subquery_planner (glob=0x224cf88, parse=0x2304c00, parent_root=0x0, tuple_fraction=0, subroot=0x7ffffaf9a9d0, config=0x2304f08) at planner.c:1196 #3 0x00000000007e6d94 in standard_planner (parse=0x2304c00, cursorOptions=0, boundParams=0x0) at planner.c:785 #4 0x00000000007e69d0 in resource_negotiator (parse=0x21feca8, cursorOptions=0, boundParams=0x0, resourceLife=QRL_ONCE, result=0x7ffffaf9ac08) at planner.c:658 #5 0x00000000007e62b4 in planner (parse=0x21feca8, cursorOptions=0, boundParams=0x0, resourceLife=QRL_ONCE) at planner.c:473 #6 0x000000000087c610 in pg_plan_query (querytree=0x21feca8, boundParams=0x0, resource_life=QRL_ONCE) at postgres.c:937 #7 0x000000000087c71b in pg_plan_queries (querytrees=0x224c560, boundParams=0x0, needSnapshot=0 ‘\000‘, resource_life=QRL_ONCE) at postgres.c:1011 #8 0x000000000087db9a in exec_simple_query (query_string=0x21fdc90 "delete from t1 where t1.id in (select id from t2);", seqServerHost=0x0, seqServerPort=-1) at postgres.c:1771 #9 0x0000000000885033 in exec_simple_query_message (firstchar=81 ‘Q‘, input_message=0x7ffffaf9b0d0) at postgres.c:6314 #10 0x00000000008829b7 in PostgresMain (argc=4, argv=0x20c5cf8, username=0x20c5c10 "brayden") at postgres.c:4873 #11 0x000000000083615a in BackendRun (port=0x2089120) at postmaster.c:5889 #12 0x000000000083560f in BackendStartup (port=0x2089120) at postmaster.c:5484 #13 0x000000000082ff00 in ServerLoop () at postmaster.c:2163 #14 0x000000000082efcb in PostmasterMain (argc=9, argv=0x2080a40) at postmaster.c:1454 #15 0x000000000075a7ef in main (argc=9, argv=0x2080a40) at main.c:226
2. 接着plan， 加入explicit motion：
(gdb) bt #0 request_explicit_motion (plan=0x226ad50, resultRelationsIdx=1, rtable=0x22e5be8) at cdbmutate.c:1430 #1 0x0000000000a621c7 in apply_motion (root=0x2304f58, plan=0x226ad50, query=0x2304c00) at cdbmutate.c:686 #2 0x0000000000a58c2a in cdbparallelize (root=0x2304f58, plan=0x226ad50, query=0x2304c00, cursorOptions=0, boundParams=0x0) at cdbllize.c:285 #3 0x00000000007e6f33 in standard_planner (parse=0x2304c00, cursorOptions=0, boundParams=0x0) at planner.c:834 #4 0x00000000007e69d0 in resource_negotiator (parse=0x21feca8, cursorOptions=0, boundParams=0x0, resourceLife=QRL_ONCE, result=0x7ffffaf9ac08) at planner.c:658 #5 0x00000000007e62b4 in planner (parse=0x21feca8, cursorOptions=0, boundParams=0x0, resourceLife=QRL_ONCE) at planner.c:473 #6 0x000000000087c610 in pg_plan_query (querytree=0x21feca8, boundParams=0x0, resource_life=QRL_ONCE) at postgres.c:937 #7 0x000000000087c71b in pg_plan_queries (querytrees=0x224c560, boundParams=0x0, needSnapshot=0 ‘\000‘, resource_life=QRL_ONCE) at postgres.c:1011 #8 0x000000000087db9a in exec_simple_query (query_string=0x21fdc90 "delete from t1 where t1.id in (select id from t2);", seqServerHost=0x0, seqServerPort=-1) at postgres.c:1771 #9 0x0000000000885033 in exec_simple_query_message (firstchar=81 ‘Q‘, input_message=0x7ffffaf9b0d0) at postgres.c:6314 #10 0x00000000008829b7 in PostgresMain (argc=4, argv=0x20c5cf8, username=0x20c5c10 "brayden") at postgres.c:4873 #11 0x000000000083615a in BackendRun (port=0x2089120) at postmaster.c:5889 #12 0x000000000083560f in BackendStartup (port=0x2089120) at postmaster.c:5484 #13 0x000000000082ff00 in ServerLoop () at postmaster.c:2163 #14 0x000000000082efcb in PostmasterMain (argc=9, argv=0x2080a40) at postmaster.c:1454 #15 0x000000000075a7ef in main (argc=9, argv=0x2080a40) at main.c:226
3. 执行， 在做projection的时候， 记录 ctid， segment id：
(gdb) bt #0 GetQEIndex () at identity.c:446 #1 0x00000000006f1404 in slot_getsysattr (slot=0x2bfc0f8, attnum=-8, isnull=0x2c4a0e9 "") at execTuples.c:1495 #2 0x00000000006e361a in slot_getattr (slot=0x2bfc0f8, attnum=-8, isnull=0x2c4a0e9 "") at ../../../src/include/executor/tuptable.h:320 #3 0x00000000006e4221 in ExecEvalVar (exprstate=0x2c49270, econtext=0x2bc7190, isNull=0x2c4a0e9 "", isDone=0x2c4967c) at execQual.c:674 #4 0x00000000006edd84 in ExecTargetList (targetlist=0x2c49210, econtext=0x2bc7190, values=0x2c4a0b8, isnull=0x2c4a0e8 "", itemIsDone=0x2c49678, isDone=0x0) at execQual.c:5565 #5 0x00000000006ee300 in ExecProject (projInfo=0x2c495e8, isDone=0x0) at execQual.c:5762 #6 0x00000000006ee808 in ExecScan (node=0x2c48d10, accessMtd=0x6f65b4 <AppendOnlyScanNext>) at execScan.c:187 #7 0x00000000006eed3c in ExecTableScanRelation (scanState=0x2c48d10) at execScan.c:460 #8 0x000000000071e703 in ExecTableScan (node=0x2c48d10) at nodeTableScan.c:59 #9 0x00000000006e1d5e in ExecProcNode (node=0x2c48d10) at execProcnode.c:1158 #10 0x000000000070a15a in ExecHashJoinOuterGetTuple (outerNode=0x2c48d10, hjstate=0x2bc2a40, hashvalue=0x7ffda17d2264) at nodeHashjoin.c:822 #11 0x000000000070956a in ExecHashJoin (node=0x2bc2a40) at nodeHashjoin.c:362 #12 0x00000000006e1e89 in ExecProcNode (node=0x2bc2a40) at execProcnode.c:1217 #13 0x0000000000711c45 in execMotionSender (node=0x2bcc5b8) at nodeMotion.c:364 #14 0x0000000000711c03 in ExecMotion (node=0x2bcc5b8) at nodeMotion.c:331 #15 0x00000000006e1f31 in ExecProcNode (node=0x2bcc5b8) at execProcnode.c:1249 #16 0x00000000006dbba2 in ExecutePlan (estate=0x2bcaa40, planstate=0x2bcc5b8, operation=CMD_SELECT, numberTuples=0, direction=ForwardScanDirection, dest=0x2c35c90) at execMain.c:3298 #17 0x00000000006d855f in ExecutorRun (queryDesc=0x2b9b210, direction=ForwardScanDirection, count=0) at execMain.c:1217 #18 0x000000000088713d in ProcessQuery (portal=0x2b990d0, stmt=0x2c21350, params=0x0, dest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:327 #19 0x000000000088a0db in PortalRunMulti (portal=0x2b990d0, isTopLevel=1 ‘\001‘, dest=0x2c35c90, altdest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:2061 #20 0x0000000000889578 in PortalRun (portal=0x2b990d0, count=9223372036854775807, isTopLevel=1 ‘\001‘, dest=0x2c35c90, altdest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:1599 #21 0x000000000087d5a4 in exec_mpp_query (query_string=0x2b750b2 "delete from t1 where t1.id in (select id from t2);", serializedQuerytree=0x0, serializedQuerytreelen=0, serializedPlantree=0x2b750e6 "+2", serializedPlantreelen=2187, serializedParams=0x0, serializedParamslen=0, serializedSliceInfo=0x2b75971 "\267\003", serializedSliceInfolen=302, serializedResource=0x2b75aec "P", serializedResourceLen=41, seqServerHost=0x2b75b15 "192.168.3.175", seqServerPort=18040, localSlice=3) at postgres.c:1508 #22 0x0000000000883128 in PostgresMain (argc=266, argv=0x2a413b0, username=0x2a22c10 "brayden") at postgres.c:5057 #23 0x000000000083615a in BackendRun (port=0x29e2520) at postmaster.c:5889 #24 0x000000000083560f in BackendStartup (port=0x29e2520) at postmaster.c:5484 #25 0x000000000082ff00 in ServerLoop () at postmaster.c:2163 ---Type <return> to continue, or q <return> to quit--- #26 0x000000000082efcb in PostmasterMain (argc=9, argv=0x29dda40) at postmaster.c:1454 #27 0x000000000075a7ef in main (argc=9, argv=0x29dda40) at main.c:226 (gdb)
4. 执行， motion send tuple， 发送给对应的sement：
(gdb) bt #0 doSendTuple (motion=0x2c21560, node=0x2bcc5b8, outerTupleSlot=0x2bfc178) at nodeMotion.c:1620 #1 0x0000000000711cbc in execMotionSender (node=0x2bcc5b8) at nodeMotion.c:400 #2 0x0000000000711c03 in ExecMotion (node=0x2bcc5b8) at nodeMotion.c:331 #3 0x00000000006e1f31 in ExecProcNode (node=0x2bcc5b8) at execProcnode.c:1249 #4 0x00000000006dbba2 in ExecutePlan (estate=0x2bcaa40, planstate=0x2bcc5b8, operation=CMD_SELECT, numberTuples=0, direction=ForwardScanDirection, dest=0x2c35c90) at execMain.c:3298 #5 0x00000000006d855f in ExecutorRun (queryDesc=0x2b9b210, direction=ForwardScanDirection, count=0) at execMain.c:1217 #6 0x000000000088713d in ProcessQuery (portal=0x2b990d0, stmt=0x2c21350, params=0x0, dest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:327 #7 0x000000000088a0db in PortalRunMulti (portal=0x2b990d0, isTopLevel=1 ‘\001‘, dest=0x2c35c90, altdest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:2061 #8 0x0000000000889578 in PortalRun (portal=0x2b990d0, count=9223372036854775807, isTopLevel=1 ‘\001‘, dest=0x2c35c90, altdest=0x2c35c90, completionTag=0x7ffda17d2a90 "") at pquery.c:1599 #9 0x000000000087d5a4 in exec_mpp_query (query_string=0x2b750b2 "delete from t1 where t1.id in (select id from t2);", serializedQuerytree=0x0, serializedQuerytreelen=0, serializedPlantree=0x2b750e6 "+2", serializedPlantreelen=2187, serializedParams=0x0, serializedParamslen=0, serializedSliceInfo=0x2b75971 "\267\003", serializedSliceInfolen=302, serializedResource=0x2b75aec "P", serializedResourceLen=41, seqServerHost=0x2b75b15 "192.168.3.175", seqServerPort=18040, localSlice=3) at postgres.c:1508 #10 0x0000000000883128 in PostgresMain (argc=266, argv=0x2a413b0, username=0x2a22c10 "brayden") at postgres.c:5057 #11 0x000000000083615a in BackendRun (port=0x29e2520) at postmaster.c:5889 #12 0x000000000083560f in BackendStartup (port=0x29e2520) at postmaster.c:5484 #13 0x000000000082ff00 in ServerLoop () at postmaster.c:2163 #14 0x000000000082efcb in PostmasterMain (argc=9, argv=0x29dda40) at postmaster.c:1454 #15 0x000000000075a7ef in main (argc=9, argv=0x29dda40) at main.c:226
