execqual.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * execQual.c
 *	  Routines to evaluate qualification and targetlist expressions
 *
 * 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/execQual.c,v 1.183.2.3 2006/03/10 01:51:34 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 *	 INTERFACE ROUTINES
 *		ExecEvalExpr	- (now a macro) evaluate an expression, return a datum
 *		ExecEvalExprSwitchContext - same, but switch into eval memory context
 *		ExecQual		- return true/false if qualification is satisfied
 *		ExecProject		- form a new tuple by projecting the given tuple
 *
 *	 NOTES
 *		The more heavily used ExecEvalExpr routines, such as ExecEvalVar(),
 *		are hotspots. Making these faster will speed up the entire system.
 *
 *		ExecProject() is used to make tuple projections.  Rather then
 *		trying to speed it up, the execution plan should be pre-processed
 *		to facilitate attribute sharing between nodes wherever possible,
 *		instead of doing needless copying.	-cim 5/31/91
 *
 *		During expression evaluation, we check_stack_depth only in
 *		ExecMakeFunctionResult rather than at every single node.  This
 *		is a compromise that trades off precision of the stack limit setting
 *		to gain speed.
 */

#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_type.h"
#include "commands/typecmds.h"
#include "executor/execdebug.h"
#include "executor/functions.h"
#include "executor/nodeSubplan.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "optimizer/planmain.h"
#include "parser/parse_expr.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/typcache.h"


/* static function decls */
static Datum ExecEvalArrayRef(ArrayRefExprState *astate,
				 ExprContext *econtext,
				 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalAggref(AggrefExprState *aggref,
			   ExprContext *econtext,
			   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
			bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalConst(ExprState *exprstate, ExprContext *econtext,
			  bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalParam(ExprState *exprstate, ExprContext *econtext,
			  bool *isNull, ExprDoneCond *isDone);
static ExprDoneCond ExecEvalFuncArgs(FunctionCallInfo fcinfo,
				 List *argList, ExprContext *econtext);
static Datum ExecMakeFunctionResultNoSets(FuncExprState *fcache,
							 ExprContext *econtext,
							 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalFunc(FuncExprState *fcache, ExprContext *econtext,
			 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalOper(FuncExprState *fcache, ExprContext *econtext,
			 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalDistinct(FuncExprState *fcache, ExprContext *econtext,
				 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalScalarArrayOp(ScalarArrayOpExprState *sstate,
					  ExprContext *econtext,
					  bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalNot(BoolExprState *notclause, ExprContext *econtext,
			bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalOr(BoolExprState *orExpr, ExprContext *econtext,
		   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext,
			bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalConvertRowtype(ConvertRowtypeExprState *cstate,
					   ExprContext *econtext,
					   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
			 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCaseTestExpr(ExprState *exprstate,
					 ExprContext *econtext,
					 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalArray(ArrayExprState *astate,
			  ExprContext *econtext,
			  bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalRow(RowExprState *rstate,
			ExprContext *econtext,
			bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCoalesce(CoalesceExprState *coalesceExpr,
				 ExprContext *econtext,
				 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalMinMax(MinMaxExprState *minmaxExpr,
			   ExprContext *econtext,
			   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalNullIf(FuncExprState *nullIfExpr,
			   ExprContext *econtext,
			   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalNullTest(GenericExprState *nstate,
				 ExprContext *econtext,
				 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalBooleanTest(GenericExprState *bstate,
					ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCoerceToDomain(CoerceToDomainState *cstate,
					   ExprContext *econtext,
					   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalCoerceToDomainValue(ExprState *exprstate,
							ExprContext *econtext,
							bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalFieldSelect(FieldSelectState *fstate,
					ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalFieldStore(FieldStoreState *fstate,
				   ExprContext *econtext,
				   bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalRelabelType(GenericExprState *exprstate,
					ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone);


/* ----------------------------------------------------------------
 *		ExecEvalExpr routines
 *
 *		Recursively evaluate a targetlist or qualification expression.
 *
 * Each of the following routines having the signature
 *		Datum ExecEvalFoo(ExprState *expression,
 *						  ExprContext *econtext,
 *						  bool *isNull,
 *						  ExprDoneCond *isDone);
 * is responsible for evaluating one type or subtype of ExprState node.
 * They are normally called via the ExecEvalExpr macro, which makes use of
 * the function pointer set up when the ExprState node was built by
 * ExecInitExpr.  (In some cases, we change this pointer later to avoid
 * re-executing one-time overhead.)
 *
 * Note: for notational simplicity we declare these functions as taking the
 * specific type of ExprState that they work on.  This requires casting when
 * assigning the function pointer in ExecInitExpr.	Be careful that the
 * function signature is declared correctly, because the cast suppresses
 * automatic checking!
 *
 *
 * All these functions share this calling convention:
 *
 * Inputs:
 *		expression: the expression state tree to evaluate
 *		econtext: evaluation context information
 *
 * Outputs:
 *		return value: Datum value of result
 *		*isNull: set to TRUE if result is NULL (actual return value is
 *				 meaningless if so); set to FALSE if non-null result
 *		*isDone: set to indicator of set-result status
 *
 * A caller that can only accept a singleton (non-set) result should pass
 * NULL for isDone; if the expression computes a set result then an error
 * will be reported via ereport.  If the caller does pass an isDone pointer
 * then *isDone is set to one of these three states:
 *		ExprSingleResult		singleton result (not a set)
 *		ExprMultipleResult		return value is one element of a set
 *		ExprEndResult			there are no more elements in the set
 * When ExprMultipleResult is returned, the caller should invoke
 * ExecEvalExpr() repeatedly until ExprEndResult is returned.  ExprEndResult
 * is returned after the last real set element.  For convenience isNull will
 * always be set TRUE when ExprEndResult is returned, but this should not be
 * taken as indicating a NULL element of the set.  Note that these return
 * conventions allow us to distinguish among a singleton NULL, a NULL element
 * of a set, and an empty set.
 *
 * The caller should already have switched into the temporary memory
 * context econtext->ecxt_per_tuple_memory.  The convenience entry point
 * ExecEvalExprSwitchContext() is provided for callers who don't prefer to
 * do the switch in an outer loop.	We do not do the switch in these routines
 * because it'd be a waste of cycles during nested expression evaluation.
 * ----------------------------------------------------------------
 */


/*----------
 *	  ExecEvalArrayRef
 *
 *	   This function takes an ArrayRef and returns the extracted Datum
 *	   if it's a simple reference, or the modified array value if it's
 *	   an array assignment (i.e., array element or slice insertion).
 *
 * NOTE: if we get a NULL result from a subexpression, we return NULL when
 * it's an array reference, or the unmodified source array when it's an
 * array assignment.  This may seem peculiar, but if we return NULL (as was
 * done in versions up through 7.0) then an assignment like
 *			UPDATE table SET arrayfield[4] = NULL
 * will result in setting the whole array to NULL, which is certainly not
 * very desirable.	By returning the source array we make the assignment
 * into a no-op, instead.  (Eventually we need to redesign arrays so that
 * individual elements can be NULL, but for now, let's try to protect users
 * from shooting themselves in the foot.)
 *
 * NOTE: we deliberately refrain from applying DatumGetArrayTypeP() here,
 * even though that might seem natural, because this code needs to support
 * both varlena arrays and fixed-length array types.  DatumGetArrayTypeP()
 * only works for the varlena kind.  The routines we call in arrayfuncs.c
 * have to know the difference (that's what they need refattrlength for).
 *----------
 */
static Datum
ExecEvalArrayRef(ArrayRefExprState *astate,
				 ExprContext *econtext,
				 bool *isNull,
				 ExprDoneCond *isDone)
{
	ArrayRef   *arrayRef = (ArrayRef *) astate->xprstate.expr;
	ArrayType  *array_source;
	ArrayType  *resultArray;
	bool		isAssignment = (arrayRef->refassgnexpr != NULL);
	bool		eisnull;
	ListCell   *l;
	int			i = 0,
				j = 0;
	IntArray	upper,
				lower;
	int		   *lIndex;

	array_source = (ArrayType *)
		DatumGetPointer(ExecEvalExpr(astate->refexpr,
									 econtext,
									 isNull,
									 isDone));

	/*
	 * If refexpr yields NULL, and it's a fetch, then result is NULL. In the
	 * assignment case, we'll cons up something below.
	 */
	if (*isNull)
	{
		if (isDone && *isDone == ExprEndResult)
			return (Datum) NULL;	/* end of set result */
		if (!isAssignment)
			return (Datum) NULL;
	}

	foreach(l, astate->refupperindexpr)
	{
		ExprState  *eltstate = (ExprState *) lfirst(l);

		if (i >= MAXDIM)
			ereport(ERROR,
					(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
					 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
							i, MAXDIM)));

		upper.indx[i++] = DatumGetInt32(ExecEvalExpr(eltstate,
													 econtext,
													 &eisnull,
													 NULL));
		/* If any index expr yields NULL, result is NULL or source array */
		if (eisnull)
		{
			if (!isAssignment)
			{
				*isNull = true;
				return (Datum) NULL;
			}
			return PointerGetDatum(array_source);
		}
	}

	if (astate->reflowerindexpr != NIL)
	{
		foreach(l, astate->reflowerindexpr)
		{
			ExprState  *eltstate = (ExprState *) lfirst(l);

			if (j >= MAXDIM)
				ereport(ERROR,
						(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
								i, MAXDIM)));

			lower.indx[j++] = DatumGetInt32(ExecEvalExpr(eltstate,
														 econtext,
														 &eisnull,
														 NULL));

			/*
			 * If any index expr yields NULL, result is NULL or source array
			 */
			if (eisnull)
			{
				if (!isAssignment)
				{
					*isNull = true;
					return (Datum) NULL;
				}
				return PointerGetDatum(array_source);
			}
		}
		/* this can't happen unless parser messed up */
		if (i != j)
			elog(ERROR, "upper and lower index lists are not same length");
		lIndex = lower.indx;
	}
	else
		lIndex = NULL;

	if (isAssignment)
	{
		Datum		sourceData;

		/*
		 * Evaluate the value to be assigned into the array.
		 *
		 * XXX At some point we'll need to look into making the old value of
		 * the array element available via CaseTestExpr, as is done by
		 * ExecEvalFieldStore.	This is not needed now but will be needed to
		 * support arrays of composite types; in an assignment to a field of
		 * an array member, the parser would generate a FieldStore that
		 * expects to fetch its input tuple via CaseTestExpr.
		 */
		sourceData = ExecEvalExpr(astate->refassgnexpr,
								  econtext,
								  &eisnull,
								  NULL);

		/*
		 * For now, can't cope with inserting NULL into an array, so make it a
		 * no-op per discussion above...
		 */
		if (eisnull)
			return PointerGetDatum(array_source);

		/*
		 * For an assignment, if all the subscripts and the input expression
		 * are non-null but the original array is null, then substitute an
		 * empty (zero-dimensional) array and proceed with the assignment.
		 * This only works for varlena arrays, though; for fixed-length array
		 * types we punt and return the null input array.
		 */
		if (*isNull)
		{
			if (astate->refattrlength > 0)		/* fixed-length array? */
				return PointerGetDatum(array_source);

			array_source = construct_md_array(NULL, 0, NULL, NULL,
											  arrayRef->refelemtype,
											  astate->refelemlength,
											  astate->refelembyval,
											  astate->refelemalign);
			*isNull = false;
		}

		if (lIndex == NULL)
			resultArray = array_set(array_source, i,
									upper.indx,
									sourceData,
									astate->refattrlength,
									astate->refelemlength,
									astate->refelembyval,
									astate->refelemalign,
									isNull);
		else
			resultArray = array_set_slice(array_source, i,
										  upper.indx, lower.indx,
								   (ArrayType *) DatumGetPointer(sourceData),
										  astate->refattrlength,
										  astate->refelemlength,
										  astate->refelembyval,
										  astate->refelemalign,
										  isNull);
		return PointerGetDatum(resultArray);
	}

	if (lIndex == NULL)
		return array_ref(array_source, i, upper.indx,
						 astate->refattrlength,
						 astate->refelemlength,
						 astate->refelembyval,
						 astate->refelemalign,
						 isNull);
	else
	{
		resultArray = array_get_slice(array_source, i,
									  upper.indx, lower.indx,
									  astate->refattrlength,
									  astate->refelemlength,
									  astate->refelembyval,
									  astate->refelemalign,
									  isNull);
		return PointerGetDatum(resultArray);
	}
}


/* ----------------------------------------------------------------
 *		ExecEvalAggref
 *
 *		Returns a Datum whose value is the value of the precomputed
 *		aggregate found in the given expression context.
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalAggref(AggrefExprState *aggref, ExprContext *econtext,
			   bool *isNull, ExprDoneCond *isDone)
{
	if (isDone)
		*isDone = ExprSingleResult;

	if (econtext->ecxt_aggvalues == NULL)		/* safety check */
		elog(ERROR, "no aggregates in this expression context");

	*isNull = econtext->ecxt_aggnulls[aggref->aggno];
	return econtext->ecxt_aggvalues[aggref->aggno];
}

/* ----------------------------------------------------------------
 *		ExecEvalVar
 *
 *		Returns a Datum whose value is the value of a range
 *		variable with respect to given expression context.
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
			bool *isNull, ExprDoneCond *isDone)
{
	Var		   *variable = (Var *) exprstate->expr;
	TupleTableSlot *slot;
	AttrNumber	attnum;

	if (isDone)
		*isDone = ExprSingleResult;

	/*
	 * Get the slot and attribute number we want
	 *
	 * The asserts check that references to system attributes only appear at
	 * the level of a relation scan; at higher levels, system attributes must
	 * be treated as ordinary variables (since we no longer have access to the