execqual.c

PostgreSQL7.4.6 for Linux

/*-------------------------------------------------------------------------
 *
 * execQual.c
 *	  Routines to evaluate qualification and targetlist expressions
 *
 * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/executor/execQual.c,v 1.150.2.1 2003/12/18 22:23:54 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
/*
 *	 INTERFACE ROUTINES
 *		ExecEvalExpr	- evaluate an expression and 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
 *		ExecEvalExpr() and ExecEvalVar() are hotspots.	making these faster
 *		will speed up the entire system.  Unfortunately they are currently
 *		implemented recursively.  Eliminating the recursion is bound to
 *		improve the speed of the executor.
 *
 *		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
 *
 */

#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 "miscadmin.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"


/* static function decls */
static Datum ExecEvalAggref(AggrefExprState *aggref,
			   ExprContext *econtext,
			   bool *isNull);
static Datum ExecEvalArrayRef(ArrayRefExprState *astate,
				 ExprContext *econtext,
				 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalVar(Var *variable, ExprContext *econtext, bool *isNull);
static Datum ExecEvalParam(Param *expression, ExprContext *econtext,
			  bool *isNull);
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);
static Datum ExecEvalScalarArrayOp(ScalarArrayOpExprState *sstate,
					  ExprContext *econtext, bool *isNull);
static ExprDoneCond ExecEvalFuncArgs(FunctionCallInfo fcinfo,
				 List *argList, ExprContext *econtext);
static Datum ExecEvalNot(BoolExprState *notclause, ExprContext *econtext,
			bool *isNull);
static Datum ExecEvalOr(BoolExprState *orExpr, ExprContext *econtext,
		   bool *isNull);
static Datum ExecEvalAnd(BoolExprState *andExpr, ExprContext *econtext,
			bool *isNull);
static Datum ExecEvalCase(CaseExprState *caseExpr, ExprContext *econtext,
			 bool *isNull, ExprDoneCond *isDone);
static Datum ExecEvalArray(ArrayExprState *astate,
			  ExprContext *econtext,
			  bool *isNull);
static Datum ExecEvalCoalesce(CoalesceExprState *coalesceExpr,
				 ExprContext *econtext,
				 bool *isNull);
static Datum ExecEvalNullIf(FuncExprState *nullIfExpr, ExprContext *econtext,
			   bool *isNull);
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(CoerceToDomainValue *conVal,
							ExprContext *econtext, bool *isNull);
static Datum ExecEvalFieldSelect(GenericExprState *fstate,
					ExprContext *econtext,
					bool *isNull, ExprDoneCond *isDone);


/*----------
 *	  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);
	List	   *elt;
	int			i = 0,
				j = 0;
	IntArray	upper,
				lower;
	int		   *lIndex;

	if (arrayRef->refexpr != NULL)
	{
		array_source = (ArrayType *)
			DatumGetPointer(ExecEvalExpr(astate->refexpr,
										 econtext,
										 isNull,
										 isDone));

		/*
		 * If refexpr yields NULL, result is always NULL, for now anyway.
		 * (This means you cannot assign to an element or slice of an
		 * array that's NULL; it'll just stay NULL.)
		 */
		if (*isNull)
			return (Datum) NULL;
	}
	else
	{
		/*
		 * Empty refexpr indicates we are doing an INSERT into an array
		 * column. For now, we just take the refassgnexpr (which the
		 * parser will have ensured is an array value) and return it
		 * as-is, ignoring any subscripts that may have been supplied in
		 * the INSERT column list. This is a kluge, but it's not real
		 * clear what the semantics ought to be...
		 */
		array_source = NULL;
	}

	foreach(elt, astate->refupperindexpr)
	{
		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((ExprState *) lfirst(elt),
													 econtext,
													 isNull,
													 NULL));
		/* If any index expr yields NULL, result is NULL or source array */
		if (*isNull)
		{
			if (!isAssignment || array_source == NULL)
				return (Datum) NULL;
			*isNull = false;
			return PointerGetDatum(array_source);
		}
	}

	if (astate->reflowerindexpr != NIL)
	{
		foreach(elt, astate->reflowerindexpr)
		{
			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((ExprState *) lfirst(elt),
														 econtext,
														 isNull,
														 NULL));

			/*
			 * If any index expr yields NULL, result is NULL or source
			 * array
			 */
			if (*isNull)
			{
				if (!isAssignment || array_source == NULL)
					return (Datum) NULL;
				*isNull = false;
				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 = ExecEvalExpr(astate->refassgnexpr,
											  econtext,
											  isNull,
											  NULL);

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

		if (array_source == NULL)
			return sourceData;	/* XXX do something else? */

		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)
{
	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(Var *variable, ExprContext *econtext, bool *isNull)
{
	Datum		result;
	TupleTableSlot *slot;
	AttrNumber	attnum;
	HeapTuple	heapTuple;
	TupleDesc	tuple_type;

	/*
	 * get the slot we want
	 */
	switch (variable->varno)
	{
		case INNER:				/* get the tuple from the inner node */
			slot = econtext->ecxt_innertuple;
			break;

		case OUTER:				/* get the tuple from the outer node */
			slot = econtext->ecxt_outertuple;
			break;

		default:				/* get the tuple from the relation being
								 * scanned */
			slot = econtext->ecxt_scantuple;
			break;
	}

	/*
	 * extract tuple information from the slot
	 */
	heapTuple = slot->val;
	tuple_type = slot->ttc_tupleDescriptor;

	attnum = variable->varattno;

	/*
	 * Some checks that are only applied for user attribute numbers
	 * (bogus system attnums will be caught inside heap_getattr).
	 */
	if (attnum > 0)
	{
		/*
		 * This assert checks that the attnum is valid.
		 */
		Assert(attnum <= tuple_type->natts &&
			   tuple_type->attrs[attnum - 1] != NULL);

		/*
		 * If the attribute's column has been dropped, we force a NULL result.
		 * This case should not happen in normal use, but it could happen if
		 * we are executing a plan cached before the column was dropped.
		 */
		if (tuple_type->attrs[attnum - 1]->attisdropped)
		{
			*isNull = true;
			return (Datum) 0;
		}

		/*
		 * This assert checks that the datatype the plan expects to get (as
		 * told by our "variable" argument) is in fact the datatype of the
		 * attribute being fetched (as seen in the current context, identified
		 * by our "econtext" argument).  Otherwise crashes are likely.
		 *
		 * Note that we can't check dropped columns, since their atttypid
		 * has been zeroed.
		 */
		Assert(variable->vartype == tuple_type->attrs[attnum - 1]->atttypid);
	}

	/*
	 * If the attribute number is invalid, then we are supposed to return
	 * the entire tuple; we give back a whole slot so that callers know
	 * what the tuple looks like.
	 *
	 * XXX this is a horrid crock: since the pointer to the slot might live
	 * longer than the current evaluation context, we are forced to copy
	 * the tuple and slot into a long-lived context --- we use the
	 * econtext's per-query memory which should be safe enough.  This
	 * represents a serious memory leak if many such tuples are processed
	 * in one command, however.  We ought to redesign the representation
	 * of whole-tuple datums so that this is not necessary.
	 *
	 * We assume it's OK to point to the existing tupleDescriptor, rather
	 * than copy that too.
	 */
	if (attnum == InvalidAttrNumber)
	{
		MemoryContext oldContext;
		TupleTableSlot *tempSlot;
		HeapTuple	tup;

		oldContext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
		tempSlot = MakeTupleTableSlot();
		tup = heap_copytuple(heapTuple);
		ExecStoreTuple(tup, tempSlot, InvalidBuffer, true);
		ExecSetSlotDescriptor(tempSlot, tuple_type, false);
		MemoryContextSwitchTo(oldContext);
		return PointerGetDatum(tempSlot);
	}

	result = heap_getattr(heapTuple,	/* tuple containing attribute */
						  attnum,		/* attribute number of desired
										 * attribute */
						  tuple_type,	/* tuple descriptor of tuple */
						  isNull);		/* return: is attribute null? */

	return result;
}

/* ----------------------------------------------------------------
 *		ExecEvalParam
 *
 *		Returns the value of a parameter.  A param node contains
 *		something like ($.name) and the expression context contains
 *		the current parameter bindings (name = "sam") (age = 34)...
 *		so our job is to find and return the appropriate datum ("sam").
 *
 *		Q: if we have a parameter ($.foo) without a binding, i.e.
 *		   there is no (foo = xxx) in the parameter list info,
 *		   is this a fatal error or should this be a "not available"
 *		   (in which case we could return NULL)?	-cim 10/13/89
 * ----------------------------------------------------------------
 */
static Datum
ExecEvalParam(Param *expression, ExprContext *econtext, bool *isNull)
{
	int			thisParamKind = expression->paramkind;
	AttrNumber	thisParamId = expression->paramid;

	if (thisParamKind == PARAM_EXEC)
	{
		/*
		 * PARAM_EXEC params (internal executor parameters) are stored in
		 * the ecxt_param_exec_vals array, and can be accessed by array
		 * index.
		 */
		ParamExecData *prm;

		prm = &(econtext->ecxt_param_exec_vals[thisParamId]);
		if (prm->execPlan != NULL)
		{
			/* Parameter not evaluated yet, so go do it */
			ExecSetParamPlan(prm->execPlan, econtext);
			/* ExecSetParamPlan should have processed this param... */
			Assert(prm->execPlan == NULL);
		}
		*isNull = prm->isnull;
		return prm->value;
	}
	else
	{
		/*
		 * All other parameter types must be sought in
		 * ecxt_param_list_info. NOTE: The last entry in the param array
		 * is always an entry with kind == PARAM_INVALID.
		 */
		ParamListInfo paramList = econtext->ecxt_param_list_info;