nodeindexscan.c

关系型数据库 Postgresql 6.5.2

 * old comments
 *		Creates the run-time state information for the node and
 *		sets the relation id to contain relevant decriptors.
 *
 *		Parameters:
 *		  node: IndexNode node produced by the planner.
 *		  estate: the execution state initialized in InitPlan.
 * ----------------------------------------------------------------
 */
bool
ExecInitIndexScan(IndexScan *node, EState *estate, Plan *parent)
{
	IndexScanState *indexstate;
	CommonScanState *scanstate;
	List	   *indxqual;
	List	   *indxid;
	int			i;
	int			numIndices;
	int			indexPtr;
	ScanKey    *scanKeys;
	int		   *numScanKeys;
	RelationPtr relationDescs;
	IndexScanDescPtr scanDescs;
	Pointer    *runtimeKeyInfo;
	bool		have_runtime_keys;
	List	   *rangeTable;
	RangeTblEntry *rtentry;
	Index		relid;
	Oid			reloid;

	Relation	currentRelation;
	HeapScanDesc currentScanDesc;
	ScanDirection direction;
	int			baseid;

	List	   *execParam = NULL;

	/* ----------------
	 *	assign execution state to node
	 * ----------------
	 */
	node->scan.plan.state = estate;

	/* --------------------------------
	 *	Part 1)  initialize scan state
	 *
	 *	create new CommonScanState for node
	 * --------------------------------
	 */
	scanstate = makeNode(CommonScanState);
/*
	scanstate->ss_ProcOuterFlag = false;
	scanstate->ss_OldRelId = 0;
*/

	node->scan.scanstate = scanstate;

	/* ----------------
	 *	assign node's base_id .. we don't use AssignNodeBaseid() because
	 *	the increment is done later on after we assign the index scan's
	 *	scanstate.	see below.
	 * ----------------
	 */
	baseid = estate->es_BaseId;
/*	  scanstate->csstate.cstate.bnode.base_id = baseid; */
	scanstate->cstate.cs_base_id = baseid;

	/* ----------------
	 *	create expression context for node
	 * ----------------
	 */
	ExecAssignExprContext(estate, &scanstate->cstate);

#define INDEXSCAN_NSLOTS 3
	/* ----------------
	 *	tuple table initialization
	 * ----------------
	 */
	ExecInitResultTupleSlot(estate, &scanstate->cstate);
	ExecInitScanTupleSlot(estate, scanstate);
/*	  ExecInitRawTupleSlot(estate, scanstate); */

	/* ----------------
	 *	initialize projection info.  result type comes from scan desc
	 *	below..
	 * ----------------
	 */
	ExecAssignProjectionInfo((Plan *) node, &scanstate->cstate);

	/* --------------------------------
	  *  Part 2)  initialize index scan state
	  *
	  *  create new IndexScanState for node
	  * --------------------------------
	  */
	indexstate = makeNode(IndexScanState);
	indexstate->iss_NumIndices = 0;
	indexstate->iss_IndexPtr = -1;
	indexstate->iss_ScanKeys = NULL;
	indexstate->iss_NumScanKeys = NULL;
	indexstate->iss_RuntimeKeyInfo = NULL;
	indexstate->iss_RelationDescs = NULL;
	indexstate->iss_ScanDescs = NULL;

	node->indxstate = indexstate;

	/* ----------------
	 *	assign base id to index scan state also
	 * ----------------
	 */
	indexstate->cstate.cs_base_id = baseid;
	baseid++;
	estate->es_BaseId = baseid;

	/* ----------------
	 *	get the index node information
	 * ----------------
	 */
	indxid = node->indxid;
	indxqual = node->indxqual;
	numIndices = length(indxid);
	indexPtr = -1;

	CXT1_printf("ExecInitIndexScan: context is %d\n", CurrentMemoryContext);

	/* ----------------
	 *	scanKeys is used to keep track of the ScanKey's. This is needed
	 *	because a single scan may use several indices and each index has
	 *	its own ScanKey.
	 * ----------------
	 */
	numScanKeys = (int *) palloc(numIndices * sizeof(int));
	scanKeys = (ScanKey *) palloc(numIndices * sizeof(ScanKey));
	relationDescs = (RelationPtr) palloc(numIndices * sizeof(Relation));
	scanDescs = (IndexScanDescPtr) palloc(numIndices * sizeof(IndexScanDesc));

	/* ----------------
	 *	initialize runtime key info.
	 * ----------------
	 */
	have_runtime_keys = false;
	runtimeKeyInfo = (Pointer *)
		palloc(numIndices * sizeof(Pointer));

	/* ----------------
	 *	build the index scan keys from the index qualification
	 * ----------------
	 */
	for (i = 0; i < numIndices; i++)
	{
		int			j;
		List	   *qual;
		int			n_keys;
		ScanKey		scan_keys;
		int		   *run_keys;

		qual = nth(i, indxqual);
		n_keys = length(qual);
		scan_keys = (n_keys <= 0) ? NULL :
			(ScanKey) palloc(n_keys * sizeof(ScanKeyData));
		run_keys = (n_keys <= 0) ? NULL :
			(int *) palloc(n_keys * sizeof(int));

		CXT1_printf("ExecInitIndexScan: context is %d\n", CurrentMemoryContext);

		/* ----------------
		 *	for each opclause in the given qual,
		 *	convert each qual's opclause into a single scan key
		 * ----------------
		 */
		for (j = 0; j < n_keys; j++)
		{
			Expr	   *clause; /* one part of index qual */
			Oper	   *op;		/* operator used in scan.. */
			Node	   *leftop; /* expr on lhs of operator */
			Node	   *rightop;/* expr on rhs ... */
			bits16		flags = 0;

			int			scanvar;/* which var identifies varattno */
			AttrNumber	varattno = 0;	/* att number used in scan */
			Oid			opid;	/* operator id used in scan */
			Datum		scanvalue = 0;	/* value used in scan (if const) */

			/* ----------------
			 *	extract clause information from the qualification
			 * ----------------
			 */
			clause = nth(j, qual);

			op = (Oper *) clause->oper;
			if (!IsA(op, Oper))
				elog(ERROR, "ExecInitIndexScan: op not an Oper!");

			opid = op->opid;

			/* ----------------
			 *	Here we figure out the contents of the index qual.
			 *	The usual case is (op var const) or (op const var)
			 *	which means we form a scan key for the attribute
			 *	listed in the var node and use the value of the const.
			 *
			 *	If we don't have a const node, then it means that
			 *	one of the var nodes refers to the "scan" tuple and
			 *	is used to determine which attribute to scan, and the
			 *	other expression is used to calculate the value used in
			 *	scanning the index.
			 *
			 *	This means our index scan's scan key is a function of
			 *	information obtained during the execution of the plan
			 *	in which case we need to recalculate the index scan key
			 *	at run time.
			 *
			 *	Hence, we set have_runtime_keys to true and then set
			 *	the appropriate flag in run_keys to LEFT_OP or RIGHT_OP.
			 *	The corresponding scan keys are recomputed at run time.
			 * ----------------
			 */

			scanvar = NO_OP;

			/* ----------------
			 *	determine information in leftop
			 * ----------------
			 */
			leftop = (Node *) get_leftop(clause);

			if (IsA(leftop, Var) &&var_is_rel((Var *) leftop))
			{
				/* ----------------
				 *	if the leftop is a "rel-var", then it means
				 *	that it is a var node which tells us which
				 *	attribute to use for our scan key.
				 * ----------------
				 */
				varattno = ((Var *) leftop)->varattno;
				scanvar = LEFT_OP;
			}
			else if (IsA(leftop, Const))
			{
				/* ----------------
				 *	if the leftop is a const node then it means
				 *	it identifies the value to place in our scan key.
				 * ----------------
				 */
				run_keys[j] = NO_OP;
				scanvalue = ((Const *) leftop)->constvalue;
			}
			else if (IsA(leftop, Param))
			{
				bool		isnull;

				/* ----------------
				 *	if the leftop is a Param node then it means
				 *	it identifies the value to place in our scan key.
				 * ----------------
				 */

				/* Life was so easy before ... subselects */
				if (((Param *) leftop)->paramkind == PARAM_EXEC)
				{
					have_runtime_keys = true;
					run_keys[j] = LEFT_OP;
					execParam = lappendi(execParam, ((Param *) leftop)->paramid);
				}
				else
				{
					scanvalue = ExecEvalParam((Param *) leftop,
										scanstate->cstate.cs_ExprContext,
											  &isnull);
					if (isnull)
						flags |= SK_ISNULL;

					run_keys[j] = NO_OP;
				}
			}
			else if (leftop != NULL &&
					 is_funcclause(leftop) &&
					 var_is_rel(lfirst(((Expr *) leftop)->args)))
			{
				/* ----------------
				 *	if the leftop is a func node then it means
				 *	it identifies the value to place in our scan key.
				 *	Since functional indices have only one attribute
				 *	the attno must always be set to 1.
				 * ----------------
				 */
				varattno = 1;
				scanvar = LEFT_OP;

			}
			else
			{
				/* ----------------
				 *	otherwise, the leftop contains information usable
				 *	at runtime to figure out the value to place in our
				 *	scan key.
				 * ----------------
				 */
				have_runtime_keys = true;
				run_keys[j] = LEFT_OP;
				scanvalue = Int32GetDatum((int32) true);
			}

			/* ----------------
			 *	now determine information in rightop
			 * ----------------
			 */
			rightop = (Node *) get_rightop(clause);

			if (IsA(rightop, Var) &&var_is_rel((Var *) rightop))
			{
				/* ----------------
				 *	here we make sure only one op identifies the
				 *	scan-attribute...
				 * ----------------
				 */
				if (scanvar == LEFT_OP)
					elog(ERROR, "ExecInitIndexScan: %s",
						 "both left and right op's are rel-vars");

				/* ----------------
				 *	if the rightop is a "rel-var", then it means
				 *	that it is a var node which tells us which
				 *	attribute to use for our scan key.
				 * ----------------
				 */
				varattno = ((Var *) rightop)->varattno;
				scanvar = RIGHT_OP;

			}
			else if (IsA(rightop, Const))
			{
				/* ----------------
				 *	if the leftop is a const node then it means
				 *	it identifies the value to place in our scan key.
				 * ----------------
				 */
				run_keys[j] = NO_OP;
				scanvalue = ((Const *) rightop)->constvalue;
			}
			else if (IsA(rightop, Param))
			{
				bool		isnull;

				/* ----------------
				 *	if the rightop is a Param node then it means
				 *	it identifies the value to place in our scan key.
				 * ----------------
				 */

				/* Life was so easy before ... subselects */
				if (((Param *) rightop)->paramkind == PARAM_EXEC)
				{
					have_runtime_keys = true;
					run_keys[j] = RIGHT_OP;
					execParam = lappendi(execParam, ((Param *) rightop)->paramid);
				}
				else
				{
					scanvalue = ExecEvalParam((Param *) rightop,
										scanstate->cstate.cs_ExprContext,
											  &isnull);
					if (isnull)
						flags |= SK_ISNULL;

					run_keys[j] = NO_OP;
				}
			}
			else if (rightop != NULL &&
					 is_funcclause(rightop) &&
					 var_is_rel(lfirst(((Expr *) rightop)->args)))
			{
				/* ----------------
				 *	if the rightop is a func node then it means
				 *	it identifies the value to place in our scan key.
				 *	Since functional indices have only one attribute
				 *	the attno must always be set to 1.
				 * ----------------
				 */
				if (scanvar == LEFT_OP)
					elog(ERROR, "ExecInitIndexScan: %s",
						 "both left and right ops are rel-vars");

				varattno = 1;
				scanvar = RIGHT_OP;

			}
			else
			{
				/* ----------------
				 *	otherwise, the leftop contains information usable
				 *	at runtime to figure out the value to place in our
				 *	scan key.
				 * ----------------
				 */
				have_runtime_keys = true;
				run_keys[j] = RIGHT_OP;
				scanvalue = Int32GetDatum((int32) true);
			}

			/* ----------------
			 *	now check that at least one op tells us the scan
			 *	attribute...
			 * ----------------
			 */
			if (scanvar == NO_OP)
				elog(ERROR, "ExecInitIndexScan: %s",
					 "neither leftop nor rightop refer to scan relation");

			/* ----------------
			 *	initialize the scan key's fields appropriately
			 * ----------------
			 */
			ScanKeyEntryInitialize(&scan_keys[j],
								   flags,
								   varattno,	/* attribute number to
												 * scan */
								   (RegProcedure) opid, /* reg proc to use */
								   (Datum) scanvalue);	/* constant */
		}

		/* ----------------
		 *	store the key information into our array.
		 * ----------------
		 */
		numScanKeys[i] = n_keys;
		scanKeys[i] = scan_keys;
		runtimeKeyInfo[i] = (Pointer) run_keys;
	}

	indexstate->iss_NumIndices = numIndices;
	indexstate->iss_IndexPtr = indexPtr;
	indexstate->iss_ScanKeys = scanKeys;
	indexstate->iss_NumScanKeys = numScanKeys;

	/* ----------------
	 *	If all of our keys have the form (op var const) , then we have no
	 *	runtime keys so we store NULL in the runtime key info.
	 *	Otherwise runtime key info contains an array of pointers
	 *	(one for each index) to arrays of flags (one for each key)
	 *	which indicate that the qual needs to be evaluated at runtime.
	 *	-cim 10/24/89
	 * ----------------
	 */
	if (have_runtime_keys)
		indexstate->iss_RuntimeKeyInfo = (Pointer) runtimeKeyInfo;
	else
		indexstate->iss_RuntimeKeyInfo = NULL;

	/* ----------------
	 *	get the range table and direction information
	 *	from the execution state (these are needed to
	 *	open the relations).
	 * ----------------
	 */
	rangeTable = estate->es_range_table;
	direction = estate->es_direction;

	/* ----------------
	 *	open the base relation
	 * ----------------
	 */
	relid = node->scan.scanrelid;
	rtentry = rt_fetch(relid, rangeTable);
	reloid = rtentry->relid;

	ExecOpenScanR(reloid,		/* relation */
				  0,			/* nkeys */
				  (ScanKey) NULL,		/* scan key */
				  0,			/* is index */
				  direction,	/* scan direction */
				  estate->es_snapshot,	/* */
				  &currentRelation,		/* return: rel desc */
				  (Pointer *) &currentScanDesc);		/* return: scan desc */

	scanstate->css_currentRelation = currentRelation;
	scanstate->css_currentScanDesc = currentScanDesc;


	/* ----------------
	 *	get the scan type from the relation descriptor.
	 * ----------------
	 */
	ExecAssignScanType(scanstate, RelationGetDescr(currentRelation));
	ExecAssignResultTypeFromTL((Plan *) node, &scanstate->cstate);

	/* ----------------
	 *	index scans don't have subtrees..
	 * ----------------
	 */
/*	  scanstate->ss_ProcOuterFlag = false; */

	/* ----------------
	 *	open the index relations and initialize
	 *	relation and scan descriptors.
	 * ----------------
	 */
	for (i = 0; i < numIndices; i++)
	{
		Oid			indexOid;

		indexOid = (Oid) nthi(i, indxid);

		if (indexOid != 0)
		{
			ExecOpenScanR(indexOid,		/* relation */
						  numScanKeys[i],		/* nkeys */
						  scanKeys[i],	/* scan key */
						  true, /* is index */
						  direction,	/* scan direction */
						  estate->es_snapshot,
						  &(relationDescs[i]),	/* return: rel desc */
						  (Pointer *) &(scanDescs[i]));
			/* return: scan desc */
		}
	}

	indexstate->iss_RelationDescs = relationDescs;
	indexstate->iss_ScanDescs = scanDescs;

	indexstate->cstate.cs_TupFromTlist = false;

	/*
	 * if there are some PARAM_EXEC in skankeys then force index rescan on
	 * first scan.
	 */
	((Plan *) node)->chgParam = execParam;

	/* ----------------
	 *	all done.
	 * ----------------
	 */
	return TRUE;
}

int
ExecCountSlotsIndexScan(IndexScan *node)
{
	return ExecCountSlotsNode(outerPlan((Plan *) node)) +
	ExecCountSlotsNode(innerPlan((Plan *) node)) + INDEXSCAN_NSLOTS;
}