greenplumn nodeNestloop 源码
greenplumn nodeNestloop 代码
文件路径：/src/backend/executor/nodeNestloop.c
/*-------------------------------------------------------------------------
*
* nodeNestloop.c
* routines to support nest-loop joins
*
* Portions Copyright (c) 2005-2008, Greenplum inc
* Portions Copyright (c) 2012-Present VMware, Inc. or its affiliates.
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeNestloop.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* ExecNestLoop - process a nestloop join of two plans
* ExecInitNestLoop - initialize the join
* ExecEndNestLoop - shut down the join
*/
#include "postgres.h"
#include "cdb/cdbvars.h"
#include "executor/execdebug.h"
#include "executor/nodeNestloop.h"
#include "optimizer/clauses.h"
#include "utils/lsyscache.h"
#include "miscadmin.h"
#include "utils/memutils.h"
extern bool Test_print_prefetch_joinqual;
static void splitJoinQualExpr(List *joinqual, List **inner_join_keys_p, List **outer_join_keys_p);
static void extractFuncExprArgs(Expr *clause, List **lclauses, List **rclauses);
/* ----------------------------------------------------------------
* ExecNestLoop(node)
*
* old comments
* Returns the tuple joined from inner and outer tuples which
* satisfies the qualification clause.
*
* It scans the inner relation to join with current outer tuple.
*
* If none is found, next tuple from the outer relation is retrieved
* and the inner relation is scanned from the beginning again to join
* with the outer tuple.
*
* NULL is returned if all the remaining outer tuples are tried and
* all fail to join with the inner tuples.
*
* NULL is also returned if there is no tuple from inner relation.
*
* Conditions:
* -- outerTuple contains current tuple from outer relation and
* the right son(inner relation) maintains "cursor" at the tuple
* returned previously.
* This is achieved by maintaining a scan position on the outer
* relation.
*
* Initial States:
* -- the outer child and the inner child
* are prepared to return the first tuple.
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecNestLoop_guts(PlanState *pstate)
{
NestLoopState *node = castNode(NestLoopState, pstate);
NestLoop *nl;
PlanState *innerPlan;
PlanState *outerPlan;
TupleTableSlot *outerTupleSlot;
TupleTableSlot *innerTupleSlot;
ExprState *joinqual;
ExprState *otherqual;
ExprContext *econtext;
ListCell *lc;
CHECK_FOR_INTERRUPTS();
/*
* get information from the node
*/
ENL1_printf("getting info from node");
nl = (NestLoop *) node->js.ps.plan;
joinqual = node->js.joinqual;
otherqual = node->js.ps.qual;
outerPlan = outerPlanState(node);
innerPlan = innerPlanState(node);
econtext = node->js.ps.ps_ExprContext;
/*
* Reset per-tuple memory context to free any expression evaluation
* storage allocated in the previous tuple cycle.
*/
ResetExprContext(econtext);
/*
* MPP-4165: My fix for MPP-3300 was correct in that we avoided
* the *deadlock* but had very unexpected (and painful)
* performance characteristics: we basically de-pipeline and
* de-parallelize execution of any query which has motion below
* us.
*
* So now prefetch_inner is set (see createplan.c) if we have *any* motion
* below us. If we don't have any motion, it doesn't matter.
*
* See motion_sanity_walker() for details on how a deadlock may occur.
*/
if (node->prefetch_inner)
{
/*
* Prefetch inner is Greenplum specific behavior.
* However, inner plan may depend on outer plan as
* outerParams. If so, we have to fake those params
* to avoid null pointer reference issue. And because
* of the nestParams, those inner results prefetched
* will be discarded (following code will rescan inner,
* even if inner's top is material node because of chgParam
* it will be re-executed too) that it is safe to fake
* nestParams here. The target is to materialize motion scan.
*/
if (nl->nestParams)
{
EState *estate = node->js.ps.state;
econtext->ecxt_outertuple = ExecInitNullTupleSlot(estate,
ExecGetResultType(outerPlan),
&TTSOpsVirtual);
fake_outer_params(&(node->js));
}
innerTupleSlot = ExecProcNode(innerPlan);
node->reset_inner = true;
econtext->ecxt_innertuple = innerTupleSlot;
if (TupIsNull(innerTupleSlot))
{
/*
* Finished one complete scan of the inner side. Mark it here
* so that we don't keep checking for inner nulls at subsequent
* iterations.
*/
node->nl_innerSideScanned = true;
}
if ((node->js.jointype == JOIN_LASJ_NOTIN) &&
(!node->nl_innerSideScanned) &&
(node->nl_InnerJoinKeys && isJoinExprNull(node->nl_InnerJoinKeys, econtext)))
{
/*
* If LASJ_NOTIN and a null was found on the inner side, all tuples
* We'll read no more from either inner or outer subtree. To keep our
* in outer sider will be treated as "not in" tuples in inner side.
*/
ENL1_printf("Found NULL tuple on the inner side, clean out");
return NULL;
}
ExecReScan(innerPlan);
ResetExprContext(econtext);
node->prefetch_inner = false;
node->reset_inner = false;
}
/*
* Prefetch JoinQual or NonJoinQual to prevent motion hazard.
*
* See ExecPrefetchQual() for details.
*/
if (node->prefetch_joinqual)
{
ExecPrefetchQual(&node->js, true);
node->prefetch_joinqual = false;
}
if (node->prefetch_qual)
{
ExecPrefetchQual(&node->js, false);
node->prefetch_qual = false;
}
/*
* Ok, everything is setup for the join so now loop until we return a
* qualifying join tuple.
*/
ENL1_printf("entering main loop");
for (;;)
{
/*
* If we don't have an outer tuple, get the next one and reset the
* inner scan.
*/
if (node->nl_NeedNewOuter)
{
ENL1_printf("getting new outer tuple");
outerTupleSlot = ExecProcNode(outerPlan);
/*
* if there are no more outer tuples, then the join is complete..
*/
if (TupIsNull(outerTupleSlot))
{
ENL1_printf("no outer tuple, ending join");
return NULL;
}
ENL1_printf("saving new outer tuple information");
econtext->ecxt_outertuple = outerTupleSlot;
node->nl_NeedNewOuter = false;
node->nl_MatchedOuter = false;
/*
* fetch the values of any outer Vars that must be passed to the
* inner scan, and store them in the appropriate PARAM_EXEC slots.
*/
foreach(lc, nl->nestParams)
{
NestLoopParam *nlp = (NestLoopParam *) lfirst(lc);
int paramno = nlp->paramno;
ParamExecData *prm;
prm = &(econtext->ecxt_param_exec_vals[paramno]);
/* Param value should be an OUTER_VAR var */
Assert(IsA(nlp->paramval, Var));
Assert(nlp->paramval->varno == OUTER_VAR);
Assert(nlp->paramval->varattno > 0);
prm->value = slot_getattr(outerTupleSlot,
nlp->paramval->varattno,
&(prm->isnull));
/* Flag parameter value as changed */
innerPlan->chgParam = bms_add_member(innerPlan->chgParam,
paramno);
}
/*
* now rescan the inner plan
*/
ENL1_printf("rescanning inner plan");
if (node->require_inner_reset || node->reset_inner)
{
ExecReScan(innerPlan);
node->reset_inner = false;
}
}
/*
* we have an outerTuple, try to get the next inner tuple.
*/
ENL1_printf("getting new inner tuple");
innerTupleSlot = ExecProcNode(innerPlan);
node->reset_inner = true;
econtext->ecxt_innertuple = innerTupleSlot;
if (TupIsNull(innerTupleSlot))
{
ENL1_printf("no inner tuple, need new outer tuple");
node->nl_NeedNewOuter = true;
/*
* Finished one complete scan of the inner side. Mark it here
* so that we don't keep checking for inner nulls at subsequent
* iterations.
*/
node->nl_innerSideScanned = true;
if (!node->nl_MatchedOuter &&
(node->js.jointype == JOIN_LEFT ||
node->js.jointype == JOIN_ANTI ||
node->js.jointype == JOIN_LASJ_NOTIN))
{
/*
* We are doing an outer join and there were no join matches
* for this outer tuple. Generate a fake join tuple with
* nulls for the inner tuple, and return it if it passes the
* non-join quals.
*/
econtext->ecxt_innertuple = node->nl_NullInnerTupleSlot;
ENL1_printf("testing qualification for outer-join tuple");
if (otherqual == NULL || ExecQual(otherqual, econtext))
{
/*
* qualification was satisfied so we project and return
* the slot containing the result tuple using
* ExecProject().
*/
ENL1_printf("qualification succeeded, projecting tuple");
return ExecProject(node->js.ps.ps_ProjInfo);
}
else
InstrCountFiltered2(node, 1);
}
/*
* Otherwise just return to top of loop for a new outer tuple.
*/
continue;
}
if ((node->js.jointype == JOIN_LASJ_NOTIN) &&
(!node->nl_innerSideScanned) &&
(node->nl_InnerJoinKeys && isJoinExprNull(node->nl_InnerJoinKeys, econtext)))
{
/*
* If LASJ_NOTIN and a null was found on the inner side, all tuples
* We'll read no more from either inner or outer subtree. To keep our
* in outer sider will be treated as "not in" tuples in inner side.
*/
ENL1_printf("Found NULL tuple on the inner side, clean out");
return NULL;
}
/*
* at this point we have a new pair of inner and outer tuples so we
* test the inner and outer tuples to see if they satisfy the node's
* qualification.
*
* Only the joinquals determine MatchedOuter status, but all quals
* must pass to actually return the tuple.
*/
ENL1_printf("testing qualification");
if((node->nl_qualResultForNull && ExecCheck(joinqual, econtext))
||(!node->nl_qualResultForNull && ExecQual(joinqual, econtext)))
{
node->nl_MatchedOuter = true;
/* In an antijoin, we never return a matched tuple */
if (node->js.jointype == JOIN_LASJ_NOTIN || node->js.jointype == JOIN_ANTI)
{
node->nl_NeedNewOuter = true;
continue; /* return to top of loop */
}
/*
* If we only need to join to the first matching inner tuple, then
* consider returning this one, but after that continue with next
* outer tuple.
*/
if (node->js.single_match)
node->nl_NeedNewOuter = true;
if (otherqual == NULL || ExecQual(otherqual, econtext))
{
/*
* qualification was satisfied so we project and return the
* slot containing the result tuple using ExecProject().
*/
ENL1_printf("qualification succeeded, projecting tuple");
return ExecProject(node->js.ps.ps_ProjInfo);
}
else
InstrCountFiltered2(node, 1);
}
else
InstrCountFiltered1(node, 1);
/*
* Tuple fails qual, so free per-tuple memory and try again.
*/
ResetExprContext(econtext);
ENL1_printf("qualification failed, looping");
}
}
static TupleTableSlot *
ExecNestLoop(PlanState *pstate)
{
TupleTableSlot *result;
result = ExecNestLoop_guts(pstate);
if (TupIsNull(result))
{
/*
* CDB: We'll read no more from inner subtree. To keep our
* sibling QEs from being starved, tell source QEs not to
* clog up the pipeline with our never-to-be-consumed
* data.
*/
ExecSquelchNode(pstate);
}
return result;
}
/* ----------------------------------------------------------------
* ExecInitNestLoop
* ----------------------------------------------------------------
*/
NestLoopState *
ExecInitNestLoop(NestLoop *node, EState *estate, int eflags)
{
NestLoopState *nlstate;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
NL1_printf("ExecInitNestLoop: %s\n",
"initializing node");
/*
* create state structure
*/
nlstate = makeNode(NestLoopState);
nlstate->js.ps.plan = (Plan *) node;
nlstate->js.ps.state = estate;
nlstate->js.ps.ExecProcNode = ExecNestLoop;
nlstate->shared_outer = node->shared_outer;
nlstate->prefetch_inner = node->join.prefetch_inner;
nlstate->prefetch_joinqual = node->join.prefetch_joinqual;
nlstate->prefetch_qual = node->join.prefetch_qual;
if (Test_print_prefetch_joinqual && nlstate->prefetch_joinqual)
elog(NOTICE,
"prefetch join qual in slice %d of plannode %d",
currentSliceId, ((Plan *) node)->plan_node_id);
/*
* reuse GUC Test_print_prefetch_joinqual to output debug information for
* prefetching non join qual
*/
if (Test_print_prefetch_joinqual && nlstate->prefetch_qual)
elog(NOTICE,
"prefetch non join qual in slice %d of plannode %d",
currentSliceId, ((Plan *) node)->plan_node_id);
/*CDB-OLAP*/
nlstate->reset_inner = false;
nlstate->require_inner_reset = !node->singleton_outer;
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &nlstate->js.ps);
/*
* initialize child nodes
*
* If we have no parameters to pass into the inner rel from the outer,
* tell the inner child that cheap rescans would be good. If we do have
* such parameters, then there is no point in REWIND support at all in the
* inner child, because it will always be rescanned with fresh parameter
* values.
*/
/*
* XXX ftian: Because share input need to make the whole thing into a tree,
* we can put the underlying share only under one shareinputscan. During execution,
* we need the shareinput node that has underlying subtree be inited/executed first.
* This means,
* 1. Init and first ExecProcNode call must be in the same order
* 2. Init order above is the same as the tree walking order in cdbmutate.c
* For nest loop join, it is more strange than others. Depends on prefetch_inner,
* the execution order may change. Handle this correctly here.
*
* Until we find a better way to handle the dependency of ShareInputScan on
* execution order, this is pretty much what we have to deal with.
*/
if (node->nestParams == NIL)
eflags |= EXEC_FLAG_REWIND;
else
eflags &= ~EXEC_FLAG_REWIND;
if (nlstate->prefetch_inner)
{
innerPlanState(nlstate) = ExecInitNode(innerPlan(node), estate, eflags);
if (!node->shared_outer)
outerPlanState(nlstate) = ExecInitNode(outerPlan(node), estate, eflags);
}
else
{
if (!node->shared_outer)
outerPlanState(nlstate) = ExecInitNode(outerPlan(node), estate, eflags);
innerPlanState(nlstate) = ExecInitNode(innerPlan(node), estate, eflags);
}
/*
* Initialize result slot, type and projection.
*/
ExecInitResultTupleSlotTL(&nlstate->js.ps, &TTSOpsVirtual);
ExecAssignProjectionInfo(&nlstate->js.ps, NULL);
/*
* initialize child expressions
*/
nlstate->js.ps.qual =
ExecInitQual(node->join.plan.qual, (PlanState *) nlstate);
nlstate->js.jointype = node->join.jointype;
if (node->join.jointype == JOIN_LASJ_NOTIN)
{
List *inner_join_keys;
List *outer_join_keys;
ListCell *lc;
/* not initialized yet */
Assert(nlstate->nl_InnerJoinKeys == NIL);
Assert(nlstate->nl_OuterJoinKeys == NIL);
splitJoinQualExpr(node->join.joinqual,
&inner_join_keys,
&outer_join_keys);
foreach(lc, inner_join_keys)
{
Expr *expr = (Expr *) lfirst(lc);
ExprState *exprstate;
exprstate = ExecInitExpr(expr, (PlanState *) nlstate);
nlstate->nl_InnerJoinKeys = lappend(nlstate->nl_InnerJoinKeys,
exprstate);
}
foreach(lc, outer_join_keys)
{
Expr *expr = (Expr *) lfirst(lc);
ExprState *exprstate;
exprstate = ExecInitExpr(expr, (PlanState *) nlstate);
nlstate->nl_OuterJoinKeys = lappend(nlstate->nl_OuterJoinKeys,
exprstate);
}
/*
* For LASJ_NOTIN, when we evaluate the join condition, we want to
* return true when one of the conditions is NULL, so we exclude
* that tuple from the output.
*/
nlstate->nl_qualResultForNull = true;
}
else
{
nlstate->nl_qualResultForNull = false;
}
if (nlstate->nl_qualResultForNull)
nlstate->js.joinqual =
ExecInitCheck(node->join.joinqual, (PlanState *) nlstate);
else
nlstate->js.joinqual =
ExecInitQual(node->join.joinqual, (PlanState *) nlstate);
/*
* detect whether we need only consider the first matching inner tuple
*/
nlstate->js.single_match = (node->join.inner_unique ||
node->join.jointype == JOIN_SEMI);
/* set up null tuples for outer joins, if needed */
switch (node->join.jointype)
{
case JOIN_INNER:
case JOIN_SEMI:
break;
case JOIN_LEFT:
case JOIN_ANTI:
case JOIN_LASJ_NOTIN:
nlstate->nl_NullInnerTupleSlot =
ExecInitNullTupleSlot(estate,
ExecGetResultType(innerPlanState(nlstate)),
&TTSOpsVirtual);
break;
default:
elog(ERROR, "unrecognized join type: %d",
(int) node->join.jointype);
}
/*
* finally, wipe the current outer tuple clean.
*/
nlstate->nl_NeedNewOuter = true;
nlstate->nl_MatchedOuter = false;
NL1_printf("ExecInitNestLoop: %s\n",
"node initialized");
return nlstate;
}
/* ----------------------------------------------------------------
* ExecEndNestLoop
*
* closes down scans and frees allocated storage
* ----------------------------------------------------------------
*/
void
ExecEndNestLoop(NestLoopState *node)
{
NL1_printf("ExecEndNestLoop: %s\n",
"ending node processing");
/*
* Free the exprcontext
*/
ExecFreeExprContext(&node->js.ps);
/*
* clean out the tuple table
*/
ExecClearTuple(node->js.ps.ps_ResultTupleSlot);
/*
* close down subplans
*/
if (!node->shared_outer)
ExecEndNode(outerPlanState(node));
ExecEndNode(innerPlanState(node));
NL1_printf("ExecEndNestLoop: %s\n",
"node processing ended");
}
/* ----------------------------------------------------------------
* ExecReScanNestLoop
* ----------------------------------------------------------------
*/
void
ExecReScanNestLoop(NestLoopState *node)
{
PlanState *outerPlan = outerPlanState(node);
/*
* If outerPlan->chgParam is not null then plan will be automatically
* re-scanned by first ExecProcNode.
*/
if (outerPlan->chgParam == NULL)
ExecReScan(outerPlan);
/*
* innerPlan is re-scanned for each new outer tuple and MUST NOT be
* re-scanned from here or you'll get troubles from inner index scans when
* outer Vars are used as run-time keys...
*/
node->nl_NeedNewOuter = true;
node->nl_MatchedOuter = false;
node->nl_innerSideScanned = false;
}
/* ----------------------------------------------------------------
* splitJoinQualExpr
*
* Deconstruct the join clauses into outer and inner argument values, so
* that we can evaluate those subexpressions separately. Note: for constant
* expression we don't need to split (MPP-21294). However, if constant expressions
* have peer splittable expressions we *do* split those.
*
* This is used for NOTIN joins, as we need to look for NULLs on both
* inner and outer side.
*
* XXX: This would be more appropriate in the planner.
* ----------------------------------------------------------------
*/
static void
splitJoinQualExpr(List *joinqual, List **inner_join_keys_p, List **outer_join_keys_p)
{
List *lclauses = NIL;
List *rclauses = NIL;
ListCell *lc;
foreach(lc, joinqual)
{
Expr *expr = (Expr *) lfirst(lc);
switch (expr->type)
{
case T_FuncExpr:
case T_OpExpr:
extractFuncExprArgs(expr, &lclauses, &rclauses);
break;
case T_BoolExpr:
{
BoolExpr *bexpr = (BoolExpr *) expr;
ListCell *argslc;
foreach(argslc, bexpr->args)
{
extractFuncExprArgs(lfirst(argslc), &lclauses, &rclauses);
}
}
break;
case T_Const:
/*
* Constant expressions do not need to be splitted into left and
* right as they don't need to be considered for NULL value special
* cases
*/
break;
default:
elog(ERROR, "unexpected expression type in NestLoopJoin qual");
}
}
*inner_join_keys_p = rclauses;
*outer_join_keys_p = lclauses;
}
/* ----------------------------------------------------------------
* extractFuncExprArgs
*
* Extract the arguments of a FuncExpr or an OpExpr and append them into two
* given lists:
* - lclauses for the left side of the expression,
* - rclauses for the right side
*
* This function is only used for LASJ. Once we find a NULL from inner side, we
* can skip the join and just return an empty set as result. This is only true
* if the equality operator is strict, that is, if a tuple from inner side is
* NULL then the equality operator returns NULL.
*
* If the number of arguments is not two, we just return leaving lclauses and
* rclauses remaining NULL. In this case, the LASJ join would be actually
* performed.
* ----------------------------------------------------------------
*/
static void
extractFuncExprArgs(Expr *clause, List **lclauses, List **rclauses)
{
if (IsA(clause, OpExpr))
{
OpExpr *opexpr = (OpExpr *) clause;
if (list_length(opexpr->args) != 2)
return;
if (!op_strict(opexpr->opno))
return;
*lclauses = lappend(*lclauses, linitial(opexpr->args));
*rclauses = lappend(*rclauses, lsecond(opexpr->args));
}
else if (IsA(clause, FuncExpr))
{
FuncExpr *fexpr = (FuncExpr *) clause;
if (list_length(fexpr->args) != 2)
return;
if (!func_strict(fexpr->funcid))
return;
*lclauses = lappend(*lclauses, linitial(fexpr->args));
*rclauses = lappend(*rclauses, lsecond(fexpr->args));
}
else if (IsA(clause, Const) && ((Const *) clause)->constisnull)
{
/*
* Greenplum will pull up not-in sublink to a specific join LASJ,
* this kind of join's joinqual might contain a NULL const here,
* for such case we do not need to split it. A case that can
* reach here is:
*
* create table t1(a int not null, b int not null);
* create table t2(a int not null, b int not null);
* explain select 1 from t1 where (NULL, b) not in (select a, b from t2);
*
* The above SQL in Greenplum will be turned in a join whose qual contains
* a bool expr (NULL = t2.a) and (t1.b = t2.b), this piece of expr will be
* evaluated to (t1.b = t2.b) and NULL by the following code path:
* subquery_planner
* -> preprocess_qual_conditions(root, (Node *) parse->jointree)
* -> preprocess_expression
* -> eval_const_expressions
* -> eval_const_expressions_mutator
*
* That is why here we have to consider const case, and only null const
* (other const cases, true or false will be simplified during the above
* code path).
*
* We do nothing here for NULL const.
*
* See Issue: https://github.com/greenplum-db/gpdb/issues/13212 for details.
*/
}
else
elog(ERROR, "unexpected join qual in JOIN_LASJ_NOTIN join");
}
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