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postgres/src/backend/executor/execMain.c

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/*-------------------------------------------------------------------------
*
* execMain.c
* top level executor interface routines
*
* INTERFACE ROUTINES
* ExecutorStart()
* ExecutorRun()
* ExecutorEnd()
*
* The old ExecutorMain() has been replaced by ExecutorStart(),
* ExecutorRun() and ExecutorEnd()
*
* These three procedures are the external interfaces to the executor.
* In each case, the query descriptor is required as an argument.
*
* ExecutorStart() must be called at the beginning of execution of any
* query plan and ExecutorEnd() should always be called at the end of
* execution of a plan.
*
* ExecutorRun accepts direction and count arguments that specify whether
* the plan is to be executed forwards, backwards, and for how many tuples.
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.258 2005/11/18 12:26:20 neilc Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/xlog.h"
#include "catalog/heap.h"
#include "catalog/namespace.h"
#include "commands/tablecmds.h"
#include "commands/trigger.h"
#include "executor/execdebug.h"
#include "executor/execdefs.h"
#include "executor/instrument.h"
#include "miscadmin.h"
#include "optimizer/clauses.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "storage/smgr.h"
#include "utils/acl.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
typedef struct execRowMark
{
Relation relation;
Index rti;
char resname[32];
} execRowMark;
typedef struct evalPlanQual
{
Index rti;
EState *estate;
PlanState *planstate;
struct evalPlanQual *next; /* stack of active PlanQual plans */
struct evalPlanQual *free; /* list of free PlanQual plans */
} evalPlanQual;
/* decls for local routines only used within this module */
static void InitPlan(QueryDesc *queryDesc, bool explainOnly);
static void initResultRelInfo(ResultRelInfo *resultRelInfo,
Index resultRelationIndex,
List *rangeTable,
CmdType operation,
bool doInstrument);
static TupleTableSlot *ExecutePlan(EState *estate, PlanState *planstate,
CmdType operation,
long numberTuples,
ScanDirection direction,
DestReceiver *dest);
static void ExecSelect(TupleTableSlot *slot,
DestReceiver *dest,
EState *estate);
static void ExecInsert(TupleTableSlot *slot, ItemPointer tupleid,
EState *estate);
static void ExecDelete(TupleTableSlot *slot, ItemPointer tupleid,
EState *estate);
static void ExecUpdate(TupleTableSlot *slot, ItemPointer tupleid,
EState *estate);
static TupleTableSlot *EvalPlanQualNext(EState *estate);
static void EndEvalPlanQual(EState *estate);
static void ExecCheckRTEPerms(RangeTblEntry *rte);
static void ExecCheckXactReadOnly(Query *parsetree);
static void EvalPlanQualStart(evalPlanQual *epq, EState *estate,
evalPlanQual *priorepq);
static void EvalPlanQualStop(evalPlanQual *epq);
/* end of local decls */
/* ----------------------------------------------------------------
* ExecutorStart
*
* This routine must be called at the beginning of any execution of any
* query plan
*
* Takes a QueryDesc previously created by CreateQueryDesc (it's not real
* clear why we bother to separate the two functions, but...). The tupDesc
* field of the QueryDesc is filled in to describe the tuples that will be
* returned, and the internal fields (estate and planstate) are set up.
*
* If explainOnly is true, we are not actually intending to run the plan,
* only to set up for EXPLAIN; so skip unwanted side-effects.
*
* NB: the CurrentMemoryContext when this is called will become the parent
* of the per-query context used for this Executor invocation.
* ----------------------------------------------------------------
*/
void
ExecutorStart(QueryDesc *queryDesc, bool explainOnly)
{
EState *estate;
MemoryContext oldcontext;
/* sanity checks: queryDesc must not be started already */
Assert(queryDesc != NULL);
Assert(queryDesc->estate == NULL);
/*
* If the transaction is read-only, we need to check if any writes are
* planned to non-temporary tables.
*/
if (XactReadOnly && !explainOnly)
ExecCheckXactReadOnly(queryDesc->parsetree);
/*
* Build EState, switch into per-query memory context for startup.
*/
estate = CreateExecutorState();
queryDesc->estate = estate;
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
/*
* Fill in parameters, if any, from queryDesc
*/
estate->es_param_list_info = queryDesc->params;
if (queryDesc->plantree->nParamExec > 0)
estate->es_param_exec_vals = (ParamExecData *)
palloc0(queryDesc->plantree->nParamExec * sizeof(ParamExecData));
/*
* Copy other important information into the EState
*/
estate->es_snapshot = queryDesc->snapshot;
estate->es_crosscheck_snapshot = queryDesc->crosscheck_snapshot;
estate->es_instrument = queryDesc->doInstrument;
/*
* Initialize the plan state tree
*/
InitPlan(queryDesc, explainOnly);
MemoryContextSwitchTo(oldcontext);
}
/* ----------------------------------------------------------------
* ExecutorRun
*
* This is the main routine of the executor module. It accepts
* the query descriptor from the traffic cop and executes the
* query plan.
*
* ExecutorStart must have been called already.
*
* If direction is NoMovementScanDirection then nothing is done
* except to start up/shut down the destination. Otherwise,
* we retrieve up to 'count' tuples in the specified direction.
*
* Note: count = 0 is interpreted as no portal limit, i.e., run to
* completion.
*
* ----------------------------------------------------------------
*/
TupleTableSlot *
ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction, long count)
{
EState *estate;
CmdType operation;
DestReceiver *dest;
TupleTableSlot *result;
MemoryContext oldcontext;
/* sanity checks */
Assert(queryDesc != NULL);
estate = queryDesc->estate;
Assert(estate != NULL);
/*
* Switch into per-query memory context
*/
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
/*
* extract information from the query descriptor and the query feature.
*/
operation = queryDesc->operation;
dest = queryDesc->dest;
/*
* startup tuple receiver
*/
estate->es_processed = 0;
estate->es_lastoid = InvalidOid;
(*dest->rStartup) (dest, operation, queryDesc->tupDesc);
/*
* run plan
*/
if (direction == NoMovementScanDirection)
result = NULL;
else
result = ExecutePlan(estate,
queryDesc->planstate,
operation,
count,
direction,
dest);
/*
* shutdown receiver
*/
(*dest->rShutdown) (dest);
MemoryContextSwitchTo(oldcontext);
return result;
}
/* ----------------------------------------------------------------
* ExecutorEnd
*
* This routine must be called at the end of execution of any
* query plan
* ----------------------------------------------------------------
*/
void
ExecutorEnd(QueryDesc *queryDesc)
{
EState *estate;
MemoryContext oldcontext;
/* sanity checks */
Assert(queryDesc != NULL);
estate = queryDesc->estate;
Assert(estate != NULL);
/*
* Switch into per-query memory context to run ExecEndPlan
*/
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
ExecEndPlan(queryDesc->planstate, estate);
/*
* Must switch out of context before destroying it
*/
MemoryContextSwitchTo(oldcontext);
/*
* Release EState and per-query memory context. This should release
* everything the executor has allocated.
*/
FreeExecutorState(estate);
/* Reset queryDesc fields that no longer point to anything */
queryDesc->tupDesc = NULL;
queryDesc->estate = NULL;
queryDesc->planstate = NULL;
}
/* ----------------------------------------------------------------
* ExecutorRewind
*
* This routine may be called on an open queryDesc to rewind it
* to the start.
* ----------------------------------------------------------------
*/
void
ExecutorRewind(QueryDesc *queryDesc)
{
EState *estate;
MemoryContext oldcontext;
/* sanity checks */
Assert(queryDesc != NULL);
estate = queryDesc->estate;
Assert(estate != NULL);
/* It's probably not sensible to rescan updating queries */
Assert(queryDesc->operation == CMD_SELECT);
/*
* Switch into per-query memory context
*/
oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
/*
* rescan plan
*/
ExecReScan(queryDesc->planstate, NULL);
MemoryContextSwitchTo(oldcontext);
}
/*
* ExecCheckRTPerms
* Check access permissions for all relations listed in a range table.
*/
void
ExecCheckRTPerms(List *rangeTable)
{
ListCell *l;
foreach(l, rangeTable)
{
RangeTblEntry *rte = lfirst(l);
ExecCheckRTEPerms(rte);
}
}
/*
* ExecCheckRTEPerms
* Check access permissions for a single RTE.
*/
static void
ExecCheckRTEPerms(RangeTblEntry *rte)
{
AclMode requiredPerms;
Oid relOid;
Oid userid;
/*
* Only plain-relation RTEs need to be checked here. Subquery RTEs are
* checked by ExecInitSubqueryScan if the subquery is still a separate
* subquery --- if it's been pulled up into our query level then the RTEs
* are in our rangetable and will be checked here. Function RTEs are
* checked by init_fcache when the function is prepared for execution.
* Join and special RTEs need no checks.
*/
if (rte->rtekind != RTE_RELATION)
return;
/*
* No work if requiredPerms is empty.
*/
requiredPerms = rte->requiredPerms;
if (requiredPerms == 0)
return;
relOid = rte->relid;
/*
* userid to check as: current user unless we have a setuid indication.
*
* Note: GetUserId() is presently fast enough that there's no harm in calling
* it separately for each RTE. If that stops being true, we could call it
* once in ExecCheckRTPerms and pass the userid down from there. But for
* now, no need for the extra clutter.
*/
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/*
* We must have *all* the requiredPerms bits, so use aclmask not aclcheck.
*/
if (pg_class_aclmask(relOid, userid, requiredPerms, ACLMASK_ALL)
!= requiredPerms)
aclcheck_error(ACLCHECK_NO_PRIV, ACL_KIND_CLASS,
get_rel_name(relOid));
}
/*
* Check that the query does not imply any writes to non-temp tables.
*/
static void
ExecCheckXactReadOnly(Query *parsetree)
{
ListCell *l;
/*
* CREATE TABLE AS or SELECT INTO?
*
* XXX should we allow this if the destination is temp?
*/
if (parsetree->into != NULL)
goto fail;
/* Fail if write permissions are requested on any non-temp table */
foreach(l, parsetree->rtable)
{
RangeTblEntry *rte = lfirst(l);
if (rte->rtekind == RTE_SUBQUERY)
{
ExecCheckXactReadOnly(rte->subquery);
continue;
}
if (rte->rtekind != RTE_RELATION)
continue;
if ((rte->requiredPerms & (~ACL_SELECT)) == 0)
continue;
if (isTempNamespace(get_rel_namespace(rte->relid)))
continue;
goto fail;
}
return;
fail:
ereport(ERROR,
(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
errmsg("transaction is read-only")));
}
/* ----------------------------------------------------------------
* InitPlan
*
* Initializes the query plan: open files, allocate storage
* and start up the rule manager
* ----------------------------------------------------------------
*/
static void
InitPlan(QueryDesc *queryDesc, bool explainOnly)
{
CmdType operation = queryDesc->operation;
Query *parseTree = queryDesc->parsetree;
Plan *plan = queryDesc->plantree;
EState *estate = queryDesc->estate;
PlanState *planstate;
List *rangeTable;
Relation intoRelationDesc;
bool do_select_into;
TupleDesc tupType;
/*
* Do permissions checks. It's sufficient to examine the query's top
* rangetable here --- subplan RTEs will be checked during
* ExecInitSubPlan().
*/
ExecCheckRTPerms(parseTree->rtable);
/*
* get information from query descriptor
*/
rangeTable = parseTree->rtable;
/*
* initialize the node's execution state
*/
estate->es_range_table = rangeTable;
/*
* if there is a result relation, initialize result relation stuff
*/
if (parseTree->resultRelation != 0 && operation != CMD_SELECT)
{
List *resultRelations = parseTree->resultRelations;
int numResultRelations;
ResultRelInfo *resultRelInfos;
if (resultRelations != NIL)
{
/*
* Multiple result relations (due to inheritance)
* parseTree->resultRelations identifies them all
*/
ResultRelInfo *resultRelInfo;
ListCell *l;
numResultRelations = list_length(resultRelations);
resultRelInfos = (ResultRelInfo *)
palloc(numResultRelations * sizeof(ResultRelInfo));
resultRelInfo = resultRelInfos;
foreach(l, resultRelations)
{
initResultRelInfo(resultRelInfo,
lfirst_int(l),
rangeTable,
operation,
estate->es_instrument);
resultRelInfo++;
}
}
else
{
/*
* Single result relation identified by parseTree->resultRelation
*/
numResultRelations = 1;
resultRelInfos = (ResultRelInfo *) palloc(sizeof(ResultRelInfo));
initResultRelInfo(resultRelInfos,
parseTree->resultRelation,
rangeTable,
operation,
estate->es_instrument);
}
estate->es_result_relations = resultRelInfos;
estate->es_num_result_relations = numResultRelations;
/* Initialize to first or only result rel */
estate->es_result_relation_info = resultRelInfos;
}
else
{
/*
* if no result relation, then set state appropriately
*/
estate->es_result_relations = NULL;
estate->es_num_result_relations = 0;
estate->es_result_relation_info = NULL;
}
/*
* Detect whether we're doing SELECT INTO. If so, set the es_into_oids
* flag appropriately so that the plan tree will be initialized with the
* correct tuple descriptors.
*/
do_select_into = false;
if (operation == CMD_SELECT && parseTree->into != NULL)
{
do_select_into = true;
estate->es_select_into = true;
estate->es_into_oids = parseTree->intoHasOids;
}
/*
* Have to lock relations selected FOR UPDATE/FOR SHARE
*/
estate->es_rowMarks = NIL;
estate->es_forUpdate = parseTree->forUpdate;
estate->es_rowNoWait = parseTree->rowNoWait;
if (parseTree->rowMarks != NIL)
{
ListCell *l;
foreach(l, parseTree->rowMarks)
{
Index rti = lfirst_int(l);
Oid relid = getrelid(rti, rangeTable);
Relation relation;
execRowMark *erm;
relation = heap_open(relid, RowShareLock);
erm = (execRowMark *) palloc(sizeof(execRowMark));
erm->relation = relation;
erm->rti = rti;
snprintf(erm->resname, sizeof(erm->resname), "ctid%u", rti);
estate->es_rowMarks = lappend(estate->es_rowMarks, erm);
}
}
/*
* initialize the executor "tuple" table. We need slots for all the plan
* nodes, plus possibly output slots for the junkfilter(s). At this point
* we aren't sure if we need junkfilters, so just add slots for them
* unconditionally. Also, if it's not a SELECT, set up a slot for use
* for trigger output tuples.
*/
{
int nSlots = ExecCountSlotsNode(plan);
if (parseTree->resultRelations != NIL)
nSlots += list_length(parseTree->resultRelations);
else
nSlots += 1;
if (operation != CMD_SELECT)
nSlots++;
estate->es_tupleTable = ExecCreateTupleTable(nSlots);
if (operation != CMD_SELECT)
estate->es_trig_tuple_slot =
ExecAllocTableSlot(estate->es_tupleTable);
}
/* mark EvalPlanQual not active */
estate->es_topPlan = plan;
estate->es_evalPlanQual = NULL;
estate->es_evTupleNull = NULL;
estate->es_evTuple = NULL;
estate->es_useEvalPlan = false;
/*
* initialize the private state information for all the nodes in the query
* tree. This opens files, allocates storage and leaves us ready to start
* processing tuples.
*/
planstate = ExecInitNode(plan, estate);
/*
* Get the tuple descriptor describing the type of tuples to return. (this
* is especially important if we are creating a relation with "SELECT
* INTO")
*/
tupType = ExecGetResultType(planstate);
/*
* Initialize the junk filter if needed. SELECT and INSERT queries need a
* filter if there are any junk attrs in the tlist. INSERT and SELECT
* INTO also need a filter if the plan may return raw disk tuples (else
* heap_insert will be scribbling on the source relation!). UPDATE and
* DELETE always need a filter, since there's always a junk 'ctid'
* attribute present --- no need to look first.
*/
{
bool junk_filter_needed = false;
ListCell *tlist;
switch (operation)
{
case CMD_SELECT:
case CMD_INSERT:
foreach(tlist, plan->targetlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(tlist);
if (tle->resjunk)
{
junk_filter_needed = true;
break;
}
}
if (!junk_filter_needed &&
(operation == CMD_INSERT || do_select_into) &&
ExecMayReturnRawTuples(planstate))
junk_filter_needed = true;
break;
case CMD_UPDATE:
case CMD_DELETE:
junk_filter_needed = true;
break;
default:
break;
}
if (junk_filter_needed)
{
/*
* If there are multiple result relations, each one needs its own
* junk filter. Note this is only possible for UPDATE/DELETE, so
* we can't be fooled by some needing a filter and some not.
*/
if (parseTree->resultRelations != NIL)
{
PlanState **appendplans;
int as_nplans;
ResultRelInfo *resultRelInfo;
int i;
/* Top plan had better be an Append here. */
Assert(IsA(plan, Append));
Assert(((Append *) plan)->isTarget);
Assert(IsA(planstate, AppendState));
appendplans = ((AppendState *) planstate)->appendplans;
as_nplans = ((AppendState *) planstate)->as_nplans;
Assert(as_nplans == estate->es_num_result_relations);
resultRelInfo = estate->es_result_relations;
for (i = 0; i < as_nplans; i++)
{
PlanState *subplan = appendplans[i];
JunkFilter *j;
j = ExecInitJunkFilter(subplan->plan->targetlist,
resultRelInfo->ri_RelationDesc->rd_att->tdhasoid,
ExecAllocTableSlot(estate->es_tupleTable));
resultRelInfo->ri_junkFilter = j;
resultRelInfo++;
}
/*
* Set active junkfilter too; at this point ExecInitAppend has
* already selected an active result relation...
*/
estate->es_junkFilter =
estate->es_result_relation_info->ri_junkFilter;
}
else
{
/* Normal case with just one JunkFilter */
JunkFilter *j;
j = ExecInitJunkFilter(planstate->plan->targetlist,
tupType->tdhasoid,
ExecAllocTableSlot(estate->es_tupleTable));
estate->es_junkFilter = j;
if (estate->es_result_relation_info)
estate->es_result_relation_info->ri_junkFilter = j;
/* For SELECT, want to return the cleaned tuple type */
if (operation == CMD_SELECT)
tupType = j->jf_cleanTupType;
}
}
else
estate->es_junkFilter = NULL;
}
/*
* If doing SELECT INTO, initialize the "into" relation. We must wait
* till now so we have the "clean" result tuple type to create the new
* table from.
*
* If EXPLAIN, skip creating the "into" relation.
*/
intoRelationDesc = NULL;
if (do_select_into && !explainOnly)
{
char *intoName;
Oid namespaceId;
AclResult aclresult;
Oid intoRelationId;
TupleDesc tupdesc;
/*
* find namespace to create in, check permissions
*/
intoName = parseTree->into->relname;
namespaceId = RangeVarGetCreationNamespace(parseTree->into);
aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(),
ACL_CREATE);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
get_namespace_name(namespaceId));
/*
* have to copy tupType to get rid of constraints
*/
tupdesc = CreateTupleDescCopy(tupType);
intoRelationId = heap_create_with_catalog(intoName,
namespaceId,
InvalidOid,
InvalidOid,
GetUserId(),
tupdesc,
RELKIND_RELATION,
false,
true,
0,
ONCOMMIT_NOOP,
allowSystemTableMods);
FreeTupleDesc(tupdesc);
/*
* Advance command counter so that the newly-created relation's
* catalog tuples will be visible to heap_open.
*/
CommandCounterIncrement();
/*
* If necessary, create a TOAST table for the into relation. Note that
* AlterTableCreateToastTable ends with CommandCounterIncrement(), so
* that the TOAST table will be visible for insertion.
*/
AlterTableCreateToastTable(intoRelationId, true);
/*
* And open the constructed table for writing.
*/
intoRelationDesc = heap_open(intoRelationId, AccessExclusiveLock);
/* use_wal off requires rd_targblock be initially invalid */
Assert(intoRelationDesc->rd_targblock == InvalidBlockNumber);
/*
* We can skip WAL-logging the insertions, unless PITR is in use.
*
* Note that for a non-temp INTO table, this is safe only because we know
* that the catalog changes above will have been WAL-logged, and so
* RecordTransactionCommit will think it needs to WAL-log the eventual
* transaction commit. Else the commit might be lost, even though all
* the data is safely fsync'd ...
*/
estate->es_into_relation_use_wal = XLogArchivingActive();
}
estate->es_into_relation_descriptor = intoRelationDesc;
queryDesc->tupDesc = tupType;
queryDesc->planstate = planstate;
}
/*
* Initialize ResultRelInfo data for one result relation
*/
static void
initResultRelInfo(ResultRelInfo *resultRelInfo,
Index resultRelationIndex,
List *rangeTable,
CmdType operation,
bool doInstrument)
{
Oid resultRelationOid;
Relation resultRelationDesc;
resultRelationOid = getrelid(resultRelationIndex, rangeTable);
resultRelationDesc = heap_open(resultRelationOid, RowExclusiveLock);
switch (resultRelationDesc->rd_rel->relkind)
{
case RELKIND_SEQUENCE:
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot change sequence \"%s\"",
RelationGetRelationName(resultRelationDesc))));
break;
case RELKIND_TOASTVALUE:
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot change TOAST relation \"%s\"",
RelationGetRelationName(resultRelationDesc))));
break;
case RELKIND_VIEW:
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot change view \"%s\"",
RelationGetRelationName(resultRelationDesc))));
break;
}
MemSet(resultRelInfo, 0, sizeof(ResultRelInfo));
resultRelInfo->type = T_ResultRelInfo;
resultRelInfo->ri_RangeTableIndex = resultRelationIndex;
resultRelInfo->ri_RelationDesc = resultRelationDesc;
resultRelInfo->ri_NumIndices = 0;
resultRelInfo->ri_IndexRelationDescs = NULL;
resultRelInfo->ri_IndexRelationInfo = NULL;
/* make a copy so as not to depend on relcache info not changing... */
resultRelInfo->ri_TrigDesc = CopyTriggerDesc(resultRelationDesc->trigdesc);
if (resultRelInfo->ri_TrigDesc)
{
int n = resultRelInfo->ri_TrigDesc->numtriggers;
resultRelInfo->ri_TrigFunctions = (FmgrInfo *)
palloc0(n * sizeof(FmgrInfo));
if (doInstrument)
resultRelInfo->ri_TrigInstrument = InstrAlloc(n);
else
resultRelInfo->ri_TrigInstrument = NULL;
}
else
{
resultRelInfo->ri_TrigFunctions = NULL;
resultRelInfo->ri_TrigInstrument = NULL;
}
resultRelInfo->ri_ConstraintExprs = NULL;
resultRelInfo->ri_junkFilter = NULL;
/*
* If there are indices on the result relation, open them and save
* descriptors in the result relation info, so that we can add new index
* entries for the tuples we add/update. We need not do this for a
* DELETE, however, since deletion doesn't affect indexes.
*/
if (resultRelationDesc->rd_rel->relhasindex &&
operation != CMD_DELETE)
ExecOpenIndices(resultRelInfo);
}
/*
* ExecContextForcesOids
*
* This is pretty grotty: when doing INSERT, UPDATE, or SELECT INTO,
* we need to ensure that result tuples have space for an OID iff they are
* going to be stored into a relation that has OIDs. In other contexts
* we are free to choose whether to leave space for OIDs in result tuples
* (we generally don't want to, but we do if a physical-tlist optimization
* is possible). This routine checks the plan context and returns TRUE if the
* choice is forced, FALSE if the choice is not forced. In the TRUE case,
* *hasoids is set to the required value.
*
* One reason this is ugly is that all plan nodes in the plan tree will emit
* tuples with space for an OID, though we really only need the topmost node
* to do so. However, node types like Sort don't project new tuples but just
* return their inputs, and in those cases the requirement propagates down
* to the input node. Eventually we might make this code smart enough to
* recognize how far down the requirement really goes, but for now we just
* make all plan nodes do the same thing if the top level forces the choice.
*
* We assume that estate->es_result_relation_info is already set up to
* describe the target relation. Note that in an UPDATE that spans an
* inheritance tree, some of the target relations may have OIDs and some not.
* We have to make the decisions on a per-relation basis as we initialize
* each of the child plans of the topmost Append plan.
*
* SELECT INTO is even uglier, because we don't have the INTO relation's
* descriptor available when this code runs; we have to look aside at a
* flag set by InitPlan().
*/
bool
ExecContextForcesOids(PlanState *planstate, bool *hasoids)
{
if (planstate->state->es_select_into)
{
*hasoids = planstate->state->es_into_oids;
return true;
}
else
{
ResultRelInfo *ri = planstate->state->es_result_relation_info;
if (ri != NULL)
{
Relation rel = ri->ri_RelationDesc;
if (rel != NULL)
{
*hasoids = rel->rd_rel->relhasoids;
return true;
}
}
}
return false;
}
/* ----------------------------------------------------------------
* ExecEndPlan
*
* Cleans up the query plan -- closes files and frees up storage
*
* NOTE: we are no longer very worried about freeing storage per se
* in this code; FreeExecutorState should be guaranteed to release all
* memory that needs to be released. What we are worried about doing
* is closing relations and dropping buffer pins. Thus, for example,
* tuple tables must be cleared or dropped to ensure pins are released.
* ----------------------------------------------------------------
*/
void
ExecEndPlan(PlanState *planstate, EState *estate)
{
ResultRelInfo *resultRelInfo;
int i;
ListCell *l;
/*
* shut down any PlanQual processing we were doing
*/
if (estate->es_evalPlanQual != NULL)
EndEvalPlanQual(estate);
/*
* shut down the node-type-specific query processing
*/
ExecEndNode(planstate);
/*
* destroy the executor "tuple" table.
*/
ExecDropTupleTable(estate->es_tupleTable, true);
estate->es_tupleTable = NULL;
/*
* close the result relation(s) if any, but hold locks until xact commit.
*/
resultRelInfo = estate->es_result_relations;
for (i = estate->es_num_result_relations; i > 0; i--)
{
/* Close indices and then the relation itself */
ExecCloseIndices(resultRelInfo);
heap_close(resultRelInfo->ri_RelationDesc, NoLock);
resultRelInfo++;
}
/*
* close the "into" relation if necessary, again keeping lock
*/
if (estate->es_into_relation_descriptor != NULL)
{
/*
* If we skipped using WAL, and it's not a temp relation, we must
* force the relation down to disk before it's safe to commit the
* transaction. This requires forcing out any dirty buffers and then
* doing a forced fsync.
*/
if (!estate->es_into_relation_use_wal &&
!estate->es_into_relation_descriptor->rd_istemp)
{
FlushRelationBuffers(estate->es_into_relation_descriptor);
smgrimmedsync(estate->es_into_relation_descriptor->rd_smgr);
}
heap_close(estate->es_into_relation_descriptor, NoLock);
}
/*
* close any relations selected FOR UPDATE/FOR SHARE, again keeping locks
*/
foreach(l, estate->es_rowMarks)
{
execRowMark *erm = lfirst(l);
heap_close(erm->relation, NoLock);
}
}
/* ----------------------------------------------------------------
* ExecutePlan
*
* processes the query plan to retrieve 'numberTuples' tuples in the
* direction specified.
*
* Retrieves all tuples if numberTuples is 0
*
* result is either a slot containing the last tuple in the case
* of a SELECT or NULL otherwise.
*
* Note: the ctid attribute is a 'junk' attribute that is removed before the
* user can see it
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecutePlan(EState *estate,
PlanState *planstate,
CmdType operation,
long numberTuples,
ScanDirection direction,
DestReceiver *dest)
{
JunkFilter *junkfilter;
TupleTableSlot *slot;
ItemPointer tupleid = NULL;
ItemPointerData tuple_ctid;
long current_tuple_count;
TupleTableSlot *result;
/*
* initialize local variables
*/
slot = NULL;
current_tuple_count = 0;
result = NULL;
/*
* Set the direction.
*/
estate->es_direction = direction;
/*
* Process BEFORE EACH STATEMENT triggers
*/
switch (operation)
{
case CMD_UPDATE:
ExecBSUpdateTriggers(estate, estate->es_result_relation_info);
break;
case CMD_DELETE:
ExecBSDeleteTriggers(estate, estate->es_result_relation_info);
break;
case CMD_INSERT:
ExecBSInsertTriggers(estate, estate->es_result_relation_info);
break;
default:
/* do nothing */
break;
}
/*
* Loop until we've processed the proper number of tuples from the plan.
*/
for (;;)
{
/* Reset the per-output-tuple exprcontext */
ResetPerTupleExprContext(estate);
/*
* Execute the plan and obtain a tuple
*/
lnext: ;
if (estate->es_useEvalPlan)
{
slot = EvalPlanQualNext(estate);
if (TupIsNull(slot))
slot = ExecProcNode(planstate);
}
else
slot = ExecProcNode(planstate);
/*
* if the tuple is null, then we assume there is nothing more to
* process so we just return null...
*/
if (TupIsNull(slot))
{
result = NULL;
break;
}
/*
* if we have a junk filter, then project a new tuple with the junk
* removed.
*
* Store this new "clean" tuple in the junkfilter's resultSlot.
* (Formerly, we stored it back over the "dirty" tuple, which is WRONG
* because that tuple slot has the wrong descriptor.)
*
* Also, extract all the junk information we need.
*/
if ((junkfilter = estate->es_junkFilter) != NULL)
{
Datum datum;
bool isNull;
/*
* extract the 'ctid' junk attribute.
*/
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
if (!ExecGetJunkAttribute(junkfilter,
slot,
"ctid",
&datum,
&isNull))
elog(ERROR, "could not find junk ctid column");
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
tupleid = (ItemPointer) DatumGetPointer(datum);
tuple_ctid = *tupleid; /* make sure we don't free the ctid!! */
tupleid = &tuple_ctid;
}
/*
* Process any FOR UPDATE or FOR SHARE locking requested.
*/
else if (estate->es_rowMarks != NIL)
{
ListCell *l;
lmark: ;
foreach(l, estate->es_rowMarks)
{
execRowMark *erm = lfirst(l);
HeapTupleData tuple;
Buffer buffer;
ItemPointerData update_ctid;
TransactionId update_xmax;
TupleTableSlot *newSlot;
LockTupleMode lockmode;
HTSU_Result test;
if (!ExecGetJunkAttribute(junkfilter,
slot,
erm->resname,
&datum,
&isNull))
elog(ERROR, "could not find junk \"%s\" column",
erm->resname);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "\"%s\" is NULL", erm->resname);
tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
if (estate->es_forUpdate)
lockmode = LockTupleExclusive;
else
lockmode = LockTupleShared;
test = heap_lock_tuple(erm->relation, &tuple, &buffer,
&update_ctid, &update_xmax,
estate->es_snapshot->curcid,
lockmode, estate->es_rowNoWait);
ReleaseBuffer(buffer);
switch (test)
{
case HeapTupleSelfUpdated:
/* treat it as deleted; do not process */
goto lnext;
case HeapTupleMayBeUpdated:
break;
case HeapTupleUpdated:
if (IsXactIsoLevelSerializable)
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
if (!ItemPointerEquals(&update_ctid,
&tuple.t_self))
{
/* updated, so look at updated version */
newSlot = EvalPlanQual(estate,
erm->rti,
&update_ctid,
update_xmax);
if (!TupIsNull(newSlot))
{
slot = newSlot;
estate->es_useEvalPlan = true;
goto lmark;
}
}
/*
* if tuple was deleted or PlanQual failed for
* updated tuple - we must not return this tuple!
*/
goto lnext;
default:
elog(ERROR, "unrecognized heap_lock_tuple status: %u",
test);
return (NULL);
}
}
}
/*
* Finally create a new "clean" tuple with all junk attributes
* removed
*/
slot = ExecFilterJunk(junkfilter, slot);
}
/*
* now that we have a tuple, do the appropriate thing with it.. either
* return it to the user, add it to a relation someplace, delete it
* from a relation, or modify some of its attributes.
*/
switch (operation)
{
case CMD_SELECT:
ExecSelect(slot, /* slot containing tuple */
dest, /* destination's tuple-receiver obj */
estate);
result = slot;
break;
case CMD_INSERT:
ExecInsert(slot, tupleid, estate);
result = NULL;
break;
case CMD_DELETE:
ExecDelete(slot, tupleid, estate);
result = NULL;
break;
case CMD_UPDATE:
ExecUpdate(slot, tupleid, estate);
result = NULL;
break;
default:
elog(ERROR, "unrecognized operation code: %d",
(int) operation);
result = NULL;
break;
}
/*
* check our tuple count.. if we've processed the proper number then
* quit, else loop again and process more tuples. Zero numberTuples
* means no limit.
*/
current_tuple_count++;
if (numberTuples && numberTuples == current_tuple_count)
break;
}
/*
* Process AFTER EACH STATEMENT triggers
*/
switch (operation)
{
case CMD_UPDATE:
ExecASUpdateTriggers(estate, estate->es_result_relation_info);
break;
case CMD_DELETE:
ExecASDeleteTriggers(estate, estate->es_result_relation_info);
break;
case CMD_INSERT:
ExecASInsertTriggers(estate, estate->es_result_relation_info);
break;
default:
/* do nothing */
break;
}
/*
* here, result is either a slot containing a tuple in the case of a
* SELECT or NULL otherwise.
*/
return result;
}
/* ----------------------------------------------------------------
* ExecSelect
*
* SELECTs are easy.. we just pass the tuple to the appropriate
* print function. The only complexity is when we do a
* "SELECT INTO", in which case we insert the tuple into
* the appropriate relation (note: this is a newly created relation
* so we don't need to worry about indices or locks.)
* ----------------------------------------------------------------
*/
static void
ExecSelect(TupleTableSlot *slot,
DestReceiver *dest,
EState *estate)
{
/*
* insert the tuple into the "into relation"
*
* XXX this probably ought to be replaced by a separate destination
*/
if (estate->es_into_relation_descriptor != NULL)
{
HeapTuple tuple;
tuple = ExecCopySlotTuple(slot);
heap_insert(estate->es_into_relation_descriptor, tuple,
estate->es_snapshot->curcid,
estate->es_into_relation_use_wal,
false); /* never any point in using FSM */
/* we know there are no indexes to update */
heap_freetuple(tuple);
IncrAppended();
}
/*
* send the tuple to the destination
*/
(*dest->receiveSlot) (slot, dest);
IncrRetrieved();
(estate->es_processed)++;
}
/* ----------------------------------------------------------------
* ExecInsert
*
* INSERTs are trickier.. we have to insert the tuple into
* the base relation and insert appropriate tuples into the
* index relations.
* ----------------------------------------------------------------
*/
static void
ExecInsert(TupleTableSlot *slot,
ItemPointer tupleid,
EState *estate)
{
HeapTuple tuple;
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
Oid newId;
/*
* get the heap tuple out of the tuple table slot, making sure we have a
* writable copy
*/
tuple = ExecMaterializeSlot(slot);
/*
* get information on the (current) result relation
*/
resultRelInfo = estate->es_result_relation_info;
resultRelationDesc = resultRelInfo->ri_RelationDesc;
/* BEFORE ROW INSERT Triggers */
if (resultRelInfo->ri_TrigDesc &&
resultRelInfo->ri_TrigDesc->n_before_row[TRIGGER_EVENT_INSERT] > 0)
{
HeapTuple newtuple;
newtuple = ExecBRInsertTriggers(estate, resultRelInfo, tuple);
if (newtuple == NULL) /* "do nothing" */
return;
if (newtuple != tuple) /* modified by Trigger(s) */
{
/*
* Put the modified tuple into a slot for convenience of routines
* below. We assume the tuple was allocated in per-tuple memory
* context, and therefore will go away by itself. The tuple table
* slot should not try to clear it.
*/
TupleTableSlot *newslot = estate->es_trig_tuple_slot;
if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
ExecSetSlotDescriptor(newslot,
slot->tts_tupleDescriptor,
false);
ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
slot = newslot;
tuple = newtuple;
}
}
/*
* Check the constraints of the tuple
*/
if (resultRelationDesc->rd_att->constr)
ExecConstraints(resultRelInfo, slot, estate);
/*
* insert the tuple
*
* Note: heap_insert returns the tid (location) of the new tuple in the
* t_self field.
*/
newId = heap_insert(resultRelationDesc, tuple,
estate->es_snapshot->curcid,
true, true);
IncrAppended();
(estate->es_processed)++;
estate->es_lastoid = newId;
setLastTid(&(tuple->t_self));
/*
* insert index entries for tuple
*/
if (resultRelInfo->ri_NumIndices > 0)
ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);
/* AFTER ROW INSERT Triggers */
ExecARInsertTriggers(estate, resultRelInfo, tuple);
}
/* ----------------------------------------------------------------
* ExecDelete
*
* DELETE is like UPDATE, except that we delete the tuple and no
* index modifications are needed
* ----------------------------------------------------------------
*/
static void
ExecDelete(TupleTableSlot *slot,
ItemPointer tupleid,
EState *estate)
{
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
HTSU_Result result;
ItemPointerData update_ctid;
TransactionId update_xmax;
/*
* get information on the (current) result relation
*/
resultRelInfo = estate->es_result_relation_info;
resultRelationDesc = resultRelInfo->ri_RelationDesc;
/* BEFORE ROW DELETE Triggers */
if (resultRelInfo->ri_TrigDesc &&
resultRelInfo->ri_TrigDesc->n_before_row[TRIGGER_EVENT_DELETE] > 0)
{
bool dodelete;
dodelete = ExecBRDeleteTriggers(estate, resultRelInfo, tupleid,
estate->es_snapshot->curcid);
if (!dodelete) /* "do nothing" */
return;
}
/*
* delete the tuple
*
* Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that the
* row to be deleted is visible to that snapshot, and throw a can't-
* serialize error if not. This is a special-case behavior needed for
* referential integrity updates in serializable transactions.
*/
ldelete:;
result = heap_delete(resultRelationDesc, tupleid,
&update_ctid, &update_xmax,
estate->es_snapshot->curcid,
estate->es_crosscheck_snapshot,
true /* wait for commit */ );
switch (result)
{
case HeapTupleSelfUpdated:
/* already deleted by self; nothing to do */
return;
case HeapTupleMayBeUpdated:
break;
case HeapTupleUpdated:
if (IsXactIsoLevelSerializable)
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
else if (!ItemPointerEquals(tupleid, &update_ctid))
{
TupleTableSlot *epqslot;
epqslot = EvalPlanQual(estate,
resultRelInfo->ri_RangeTableIndex,
&update_ctid,
update_xmax);
if (!TupIsNull(epqslot))
{
*tupleid = update_ctid;
goto ldelete;
}
}
/* tuple already deleted; nothing to do */
return;
default:
elog(ERROR, "unrecognized heap_delete status: %u", result);
return;
}
IncrDeleted();
(estate->es_processed)++;
/*
* Note: Normally one would think that we have to delete index tuples
* associated with the heap tuple now..
*
* ... but in POSTGRES, we have no need to do this because the vacuum daemon
* automatically opens an index scan and deletes index tuples when it
* finds deleted heap tuples. -cim 9/27/89
*/
/* AFTER ROW DELETE Triggers */
ExecARDeleteTriggers(estate, resultRelInfo, tupleid);
}
/* ----------------------------------------------------------------
* ExecUpdate
*
* note: we can't run UPDATE queries with transactions
* off because UPDATEs are actually INSERTs and our
* scan will mistakenly loop forever, updating the tuple
* it just inserted.. This should be fixed but until it
* is, we don't want to get stuck in an infinite loop
* which corrupts your database..
* ----------------------------------------------------------------
*/
static void
ExecUpdate(TupleTableSlot *slot,
ItemPointer tupleid,
EState *estate)
{
HeapTuple tuple;
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
HTSU_Result result;
ItemPointerData update_ctid;
TransactionId update_xmax;
/*
* abort the operation if not running transactions
*/
if (IsBootstrapProcessingMode())
elog(ERROR, "cannot UPDATE during bootstrap");
/*
* get the heap tuple out of the tuple table slot, making sure we have a
* writable copy
*/
tuple = ExecMaterializeSlot(slot);
/*
* get information on the (current) result relation
*/
resultRelInfo = estate->es_result_relation_info;
resultRelationDesc = resultRelInfo->ri_RelationDesc;
/* BEFORE ROW UPDATE Triggers */
if (resultRelInfo->ri_TrigDesc &&
resultRelInfo->ri_TrigDesc->n_before_row[TRIGGER_EVENT_UPDATE] > 0)
{
HeapTuple newtuple;
newtuple = ExecBRUpdateTriggers(estate, resultRelInfo,
tupleid, tuple,
estate->es_snapshot->curcid);
if (newtuple == NULL) /* "do nothing" */
return;
if (newtuple != tuple) /* modified by Trigger(s) */
{
/*
* Put the modified tuple into a slot for convenience of routines
* below. We assume the tuple was allocated in per-tuple memory
* context, and therefore will go away by itself. The tuple table
* slot should not try to clear it.
*/
TupleTableSlot *newslot = estate->es_trig_tuple_slot;
if (newslot->tts_tupleDescriptor != slot->tts_tupleDescriptor)
ExecSetSlotDescriptor(newslot,
slot->tts_tupleDescriptor,
false);
ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
slot = newslot;
tuple = newtuple;
}
}
/*
* Check the constraints of the tuple
*
* If we generate a new candidate tuple after EvalPlanQual testing, we must
* loop back here and recheck constraints. (We don't need to redo
* triggers, however. If there are any BEFORE triggers then trigger.c
* will have done heap_lock_tuple to lock the correct tuple, so there's no
* need to do them again.)
*/
lreplace:;
if (resultRelationDesc->rd_att->constr)
ExecConstraints(resultRelInfo, slot, estate);
/*
* replace the heap tuple
*
* Note: if es_crosscheck_snapshot isn't InvalidSnapshot, we check that the
* row to be updated is visible to that snapshot, and throw a can't-
* serialize error if not. This is a special-case behavior needed for
* referential integrity updates in serializable transactions.
*/
result = heap_update(resultRelationDesc, tupleid, tuple,
&update_ctid, &update_xmax,
estate->es_snapshot->curcid,
estate->es_crosscheck_snapshot,
true /* wait for commit */ );
switch (result)
{
case HeapTupleSelfUpdated:
/* already deleted by self; nothing to do */
return;
case HeapTupleMayBeUpdated:
break;
case HeapTupleUpdated:
if (IsXactIsoLevelSerializable)
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
else if (!ItemPointerEquals(tupleid, &update_ctid))
{
TupleTableSlot *epqslot;
epqslot = EvalPlanQual(estate,
resultRelInfo->ri_RangeTableIndex,
&update_ctid,
update_xmax);
if (!TupIsNull(epqslot))
{
*tupleid = update_ctid;
slot = ExecFilterJunk(estate->es_junkFilter, epqslot);
tuple = ExecMaterializeSlot(slot);
goto lreplace;
}
}
/* tuple already deleted; nothing to do */
return;
default:
elog(ERROR, "unrecognized heap_update status: %u", result);
return;
}
IncrReplaced();
(estate->es_processed)++;
/*
* Note: instead of having to update the old index tuples associated with
* the heap tuple, all we do is form and insert new index tuples. This is
* because UPDATEs are actually DELETEs and INSERTs, and index tuple
* deletion is done automagically by the vacuum daemon. All we do is
* insert new index tuples. -cim 9/27/89
*/
/*
* insert index entries for tuple
*
* Note: heap_update returns the tid (location) of the new tuple in the
* t_self field.
*/
if (resultRelInfo->ri_NumIndices > 0)
ExecInsertIndexTuples(slot, &(tuple->t_self), estate, false);
/* AFTER ROW UPDATE Triggers */
ExecARUpdateTriggers(estate, resultRelInfo, tupleid, tuple);
}
static const char *
ExecRelCheck(ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, EState *estate)
{
Relation rel = resultRelInfo->ri_RelationDesc;
int ncheck = rel->rd_att->constr->num_check;
ConstrCheck *check = rel->rd_att->constr->check;
ExprContext *econtext;
MemoryContext oldContext;
List *qual;
int i;
/*
* If first time through for this result relation, build expression
* nodetrees for rel's constraint expressions. Keep them in the per-query
* memory context so they'll survive throughout the query.
*/
if (resultRelInfo->ri_ConstraintExprs == NULL)
{
oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
resultRelInfo->ri_ConstraintExprs =
(List **) palloc(ncheck * sizeof(List *));
for (i = 0; i < ncheck; i++)
{
/* ExecQual wants implicit-AND form */
qual = make_ands_implicit(stringToNode(check[i].ccbin));
resultRelInfo->ri_ConstraintExprs[i] = (List *)
ExecPrepareExpr((Expr *) qual, estate);
}
MemoryContextSwitchTo(oldContext);
}
/*
* We will use the EState's per-tuple context for evaluating constraint
* expressions (creating it if it's not already there).
*/
econtext = GetPerTupleExprContext(estate);
/* Arrange for econtext's scan tuple to be the tuple under test */
econtext->ecxt_scantuple = slot;
/* And evaluate the constraints */
for (i = 0; i < ncheck; i++)
{
qual = resultRelInfo->ri_ConstraintExprs[i];
/*
* NOTE: SQL92 specifies that a NULL result from a constraint
* expression is not to be treated as a failure. Therefore, tell
* ExecQual to return TRUE for NULL.
*/
if (!ExecQual(qual, econtext, true))
return check[i].ccname;
}
/* NULL result means no error */
return NULL;
}
void
ExecConstraints(ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, EState *estate)
{
Relation rel = resultRelInfo->ri_RelationDesc;
TupleConstr *constr = rel->rd_att->constr;
Assert(constr);
if (constr->has_not_null)
{
int natts = rel->rd_att->natts;
int attrChk;
for (attrChk = 1; attrChk <= natts; attrChk++)
{
if (rel->rd_att->attrs[attrChk - 1]->attnotnull &&
slot_attisnull(slot, attrChk))
ereport(ERROR,
(errcode(ERRCODE_NOT_NULL_VIOLATION),
errmsg("null value in column \"%s\" violates not-null constraint",
NameStr(rel->rd_att->attrs[attrChk - 1]->attname))));
}
}
if (constr->num_check > 0)
{
const char *failed;
if ((failed = ExecRelCheck(resultRelInfo, slot, estate)) != NULL)
ereport(ERROR,
(errcode(ERRCODE_CHECK_VIOLATION),
errmsg("new row for relation \"%s\" violates check constraint \"%s\"",
RelationGetRelationName(rel), failed)));
}
}
/*
* Check a modified tuple to see if we want to process its updated version
* under READ COMMITTED rules.
*
* See backend/executor/README for some info about how this works.
*
* estate - executor state data
* rti - rangetable index of table containing tuple
* *tid - t_ctid from the outdated tuple (ie, next updated version)
* priorXmax - t_xmax from the outdated tuple
*
* *tid is also an output parameter: it's modified to hold the TID of the
* latest version of the tuple (note this may be changed even on failure)
*
* Returns a slot containing the new candidate update/delete tuple, or
* NULL if we determine we shouldn't process the row.
*/
TupleTableSlot *
EvalPlanQual(EState *estate, Index rti,
ItemPointer tid, TransactionId priorXmax)
{
evalPlanQual *epq;
EState *epqstate;
Relation relation;
HeapTupleData tuple;
HeapTuple copyTuple = NULL;
bool endNode;
Assert(rti != 0);
/*
* find relation containing target tuple
*/
if (estate->es_result_relation_info != NULL &&
estate->es_result_relation_info->ri_RangeTableIndex == rti)
relation = estate->es_result_relation_info->ri_RelationDesc;
else
{
ListCell *l;
relation = NULL;
foreach(l, estate->es_rowMarks)
{
if (((execRowMark *) lfirst(l))->rti == rti)
{
relation = ((execRowMark *) lfirst(l))->relation;
break;
}
}
if (relation == NULL)
elog(ERROR, "could not find RowMark for RT index %u", rti);
}
/*
* fetch tid tuple
*
* Loop here to deal with updated or busy tuples
*/
tuple.t_self = *tid;
for (;;)
{
Buffer buffer;
if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, true, NULL))
{
/*
* If xmin isn't what we're expecting, the slot must have been
* recycled and reused for an unrelated tuple. This implies that
* the latest version of the row was deleted, so we need do
* nothing. (Should be safe to examine xmin without getting
* buffer's content lock, since xmin never changes in an existing
* tuple.)
*/
if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
priorXmax))
{
ReleaseBuffer(buffer);
return NULL;
}
/* otherwise xmin should not be dirty... */
if (TransactionIdIsValid(SnapshotDirty->xmin))
elog(ERROR, "t_xmin is uncommitted in tuple to be updated");
/*
* If tuple is being updated by other transaction then we have to
* wait for its commit/abort.
*/
if (TransactionIdIsValid(SnapshotDirty->xmax))
{
ReleaseBuffer(buffer);
XactLockTableWait(SnapshotDirty->xmax);
continue; /* loop back to repeat heap_fetch */
}
/*
* We got tuple - now copy it for use by recheck query.
*/
copyTuple = heap_copytuple(&tuple);
ReleaseBuffer(buffer);
break;
}
/*
* If the referenced slot was actually empty, the latest version of
* the row must have been deleted, so we need do nothing.
*/
if (tuple.t_data == NULL)
{
ReleaseBuffer(buffer);
return NULL;
}
/*
* As above, if xmin isn't what we're expecting, do nothing.
*/
if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
priorXmax))
{
ReleaseBuffer(buffer);
return NULL;
}
/*
* If we get here, the tuple was found but failed SnapshotDirty.
* Assuming the xmin is either a committed xact or our own xact (as it
* certainly should be if we're trying to modify the tuple), this must
* mean that the row was updated or deleted by either a committed xact
* or our own xact. If it was deleted, we can ignore it; if it was
* updated then chain up to the next version and repeat the whole
* test.
*
* As above, it should be safe to examine xmax and t_ctid without the
* buffer content lock, because they can't be changing.
*/
if (ItemPointerEquals(&tuple.t_self, &tuple.t_data->t_ctid))
{
/* deleted, so forget about it */
ReleaseBuffer(buffer);
return NULL;
}
/* updated, so look at the updated row */
tuple.t_self = tuple.t_data->t_ctid;
/* updated row should have xmin matching this xmax */
priorXmax = HeapTupleHeaderGetXmax(tuple.t_data);
ReleaseBuffer(buffer);
/* loop back to fetch next in chain */
}
/*
* For UPDATE/DELETE we have to return tid of actual row we're executing
* PQ for.
*/
*tid = tuple.t_self;
/*
* Need to run a recheck subquery. Find or create a PQ stack entry.
*/
epq = estate->es_evalPlanQual;
endNode = true;
if (epq != NULL && epq->rti == 0)
{
/* Top PQ stack entry is idle, so re-use it */
Assert(!(estate->es_useEvalPlan) && epq->next == NULL);
epq->rti = rti;
endNode = false;
}
/*
* If this is request for another RTE - Ra, - then we have to check wasn't
* PlanQual requested for Ra already and if so then Ra' row was updated
* again and we have to re-start old execution for Ra and forget all what
* we done after Ra was suspended. Cool? -:))
*/
if (epq != NULL && epq->rti != rti &&
epq->estate->es_evTuple[rti - 1] != NULL)
{
do
{
evalPlanQual *oldepq;
/* stop execution */
EvalPlanQualStop(epq);
/* pop previous PlanQual from the stack */
oldepq = epq->next;
Assert(oldepq && oldepq->rti != 0);
/* push current PQ to freePQ stack */
oldepq->free = epq;
epq = oldepq;
estate->es_evalPlanQual = epq;
} while (epq->rti != rti);
}
/*
* If we are requested for another RTE then we have to suspend execution
* of current PlanQual and start execution for new one.
*/
if (epq == NULL || epq->rti != rti)
{
/* try to reuse plan used previously */
evalPlanQual *newepq = (epq != NULL) ? epq->free : NULL;
if (newepq == NULL) /* first call or freePQ stack is empty */
{
newepq = (evalPlanQual *) palloc0(sizeof(evalPlanQual));
newepq->free = NULL;
newepq->estate = NULL;
newepq->planstate = NULL;
}
else
{
/* recycle previously used PlanQual */
Assert(newepq->estate == NULL);
epq->free = NULL;
}
/* push current PQ to the stack */
newepq->next = epq;
epq = newepq;
estate->es_evalPlanQual = epq;
epq->rti = rti;
endNode = false;
}
Assert(epq->rti == rti);
/*
* Ok - we're requested for the same RTE. Unfortunately we still have to
* end and restart execution of the plan, because ExecReScan wouldn't
* ensure that upper plan nodes would reset themselves. We could make
* that work if insertion of the target tuple were integrated with the
* Param mechanism somehow, so that the upper plan nodes know that their
* children's outputs have changed.
*
* Note that the stack of free evalPlanQual nodes is quite useless at the
* moment, since it only saves us from pallocing/releasing the
* evalPlanQual nodes themselves. But it will be useful once we implement
* ReScan instead of end/restart for re-using PlanQual nodes.
*/
if (endNode)
{
/* stop execution */
EvalPlanQualStop(epq);
}
/*
* Initialize new recheck query.
*
* Note: if we were re-using PlanQual plans via ExecReScan, we'd need to
* instead copy down changeable state from the top plan (including
* es_result_relation_info, es_junkFilter) and reset locally changeable
* state in the epq (including es_param_exec_vals, es_evTupleNull).
*/
EvalPlanQualStart(epq, estate, epq->next);
/*
* free old RTE' tuple, if any, and store target tuple where relation's
* scan node will see it
*/
epqstate = epq->estate;
if (epqstate->es_evTuple[rti - 1] != NULL)
heap_freetuple(epqstate->es_evTuple[rti - 1]);
epqstate->es_evTuple[rti - 1] = copyTuple;
return EvalPlanQualNext(estate);
}
static TupleTableSlot *
EvalPlanQualNext(EState *estate)
{
evalPlanQual *epq = estate->es_evalPlanQual;
MemoryContext oldcontext;
TupleTableSlot *slot;
Assert(epq->rti != 0);
lpqnext:;
oldcontext = MemoryContextSwitchTo(epq->estate->es_query_cxt);
slot = ExecProcNode(epq->planstate);
MemoryContextSwitchTo(oldcontext);
/*
* No more tuples for this PQ. Continue previous one.
*/
if (TupIsNull(slot))
{
evalPlanQual *oldepq;
/* stop execution */
EvalPlanQualStop(epq);
/* pop old PQ from the stack */
oldepq = epq->next;
if (oldepq == NULL)
{
/* this is the first (oldest) PQ - mark as free */
epq->rti = 0;
estate->es_useEvalPlan = false;
/* and continue Query execution */
return (NULL);
}
Assert(oldepq->rti != 0);
/* push current PQ to freePQ stack */
oldepq->free = epq;
epq = oldepq;
estate->es_evalPlanQual = epq;
goto lpqnext;
}
return (slot);
}
static void
EndEvalPlanQual(EState *estate)
{
evalPlanQual *epq = estate->es_evalPlanQual;
if (epq->rti == 0) /* plans already shutdowned */
{
Assert(epq->next == NULL);
return;
}
for (;;)
{
evalPlanQual *oldepq;
/* stop execution */
EvalPlanQualStop(epq);
/* pop old PQ from the stack */
oldepq = epq->next;
if (oldepq == NULL)
{
/* this is the first (oldest) PQ - mark as free */
epq->rti = 0;
estate->es_useEvalPlan = false;
break;
}
Assert(oldepq->rti != 0);
/* push current PQ to freePQ stack */
oldepq->free = epq;
epq = oldepq;
estate->es_evalPlanQual = epq;
}
}
/*
* Start execution of one level of PlanQual.
*
* This is a cut-down version of ExecutorStart(): we copy some state from
* the top-level estate rather than initializing it fresh.
*/
static void
EvalPlanQualStart(evalPlanQual *epq, EState *estate, evalPlanQual *priorepq)
{
EState *epqstate;
int rtsize;
MemoryContext oldcontext;
rtsize = list_length(estate->es_range_table);
epq->estate = epqstate = CreateExecutorState();
oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);
/*
* The epqstates share the top query's copy of unchanging state such as
* the snapshot, rangetable, result-rel info, and external Param info.
* They need their own copies of local state, including a tuple table,
* es_param_exec_vals, etc.
*/
epqstate->es_direction = ForwardScanDirection;
epqstate->es_snapshot = estate->es_snapshot;
epqstate->es_crosscheck_snapshot = estate->es_crosscheck_snapshot;
epqstate->es_range_table = estate->es_range_table;
epqstate->es_result_relations = estate->es_result_relations;
epqstate->es_num_result_relations = estate->es_num_result_relations;
epqstate->es_result_relation_info = estate->es_result_relation_info;
epqstate->es_junkFilter = estate->es_junkFilter;
epqstate->es_into_relation_descriptor = estate->es_into_relation_descriptor;
epqstate->es_into_relation_use_wal = estate->es_into_relation_use_wal;
epqstate->es_param_list_info = estate->es_param_list_info;
if (estate->es_topPlan->nParamExec > 0)
epqstate->es_param_exec_vals = (ParamExecData *)
palloc0(estate->es_topPlan->nParamExec * sizeof(ParamExecData));
epqstate->es_rowMarks = estate->es_rowMarks;
epqstate->es_forUpdate = estate->es_forUpdate;
epqstate->es_rowNoWait = estate->es_rowNoWait;
epqstate->es_instrument = estate->es_instrument;
epqstate->es_select_into = estate->es_select_into;
epqstate->es_into_oids = estate->es_into_oids;
epqstate->es_topPlan = estate->es_topPlan;
/*
* Each epqstate must have its own es_evTupleNull state, but all the stack
* entries share es_evTuple state. This allows sub-rechecks to inherit
* the value being examined by an outer recheck.
*/
epqstate->es_evTupleNull = (bool *) palloc0(rtsize * sizeof(bool));
if (priorepq == NULL)
/* first PQ stack entry */
epqstate->es_evTuple = (HeapTuple *)
palloc0(rtsize * sizeof(HeapTuple));
else
/* later stack entries share the same storage */
epqstate->es_evTuple = priorepq->estate->es_evTuple;
epqstate->es_tupleTable =
ExecCreateTupleTable(estate->es_tupleTable->size);
epq->planstate = ExecInitNode(estate->es_topPlan, epqstate);
MemoryContextSwitchTo(oldcontext);
}
/*
* End execution of one level of PlanQual.
*
* This is a cut-down version of ExecutorEnd(); basically we want to do most
* of the normal cleanup, but *not* close result relations (which we are
* just sharing from the outer query).
*/
static void
EvalPlanQualStop(evalPlanQual *epq)
{
EState *epqstate = epq->estate;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(epqstate->es_query_cxt);
ExecEndNode(epq->planstate);
ExecDropTupleTable(epqstate->es_tupleTable, true);
epqstate->es_tupleTable = NULL;
if (epqstate->es_evTuple[epq->rti - 1] != NULL)
{
heap_freetuple(epqstate->es_evTuple[epq->rti - 1]);
epqstate->es_evTuple[epq->rti - 1] = NULL;
}
MemoryContextSwitchTo(oldcontext);
FreeExecutorState(epqstate);
epq->estate = NULL;
epq->planstate = NULL;
}
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