nodeindexscan.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

}

/* ----------------------------------------------------------------
 *		ExecIndexRestrPos
 * ----------------------------------------------------------------
 */
void
ExecIndexRestrPos(IndexScanState *node)
{
	index_restrpos(node->iss_ScanDesc);
}

/* ----------------------------------------------------------------
 *		ExecInitIndexScan
 *
 *		Initializes the index scan's state information, creates
 *		scan keys, and opens the base and index relations.
 *
 *		Note: index scans have 2 sets of state information because
 *			  we have to keep track of the base relation and the
 *			  index relation.
 * ----------------------------------------------------------------
 */
IndexScanState *
ExecInitIndexScan(IndexScan *node, EState *estate)
{
	IndexScanState *indexstate;
	ScanKey		scanKeys;
	int			numScanKeys;
	ExprState **runtimeKeyInfo;
	bool		have_runtime_keys;
	RangeTblEntry *rtentry;
	Index		relid;
	Oid			reloid;
	Relation	currentRelation;

	/*
	 * create state structure
	 */
	indexstate = makeNode(IndexScanState);
	indexstate->ss.ps.plan = (Plan *) node;
	indexstate->ss.ps.state = estate;

	/*
	 * Miscellaneous initialization
	 *
	 * create expression context for node
	 */
	ExecAssignExprContext(estate, &indexstate->ss.ps);

	/*
	 * initialize child expressions
	 *
	 * Note: we don't initialize all of the indexqual expression, only the
	 * sub-parts corresponding to runtime keys (see below).  The indexqualorig
	 * expression is always initialized even though it will only be used in
	 * some uncommon cases --- would be nice to improve that.  (Problem is
	 * that any SubPlans present in the expression must be found now...)
	 */
	indexstate->ss.ps.targetlist = (List *)
		ExecInitExpr((Expr *) node->scan.plan.targetlist,
					 (PlanState *) indexstate);
	indexstate->ss.ps.qual = (List *)
		ExecInitExpr((Expr *) node->scan.plan.qual,
					 (PlanState *) indexstate);
	indexstate->indexqualorig = (List *)
		ExecInitExpr((Expr *) node->indexqualorig,
					 (PlanState *) indexstate);

#define INDEXSCAN_NSLOTS 2

	/*
	 * tuple table initialization
	 */
	ExecInitResultTupleSlot(estate, &indexstate->ss.ps);
	ExecInitScanTupleSlot(estate, &indexstate->ss);

	/*
	 * Initialize index-specific scan state
	 */
	indexstate->iss_RuntimeKeysReady = false;

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

	/*
	 * build the index scan keys from the index qualification
	 */
	have_runtime_keys =
		ExecIndexBuildScanKeys((PlanState *) indexstate,
							   node->indexqual,
							   node->indexstrategy,
							   node->indexsubtype,
							   &runtimeKeyInfo,
							   &scanKeys,
							   &numScanKeys);

	indexstate->iss_RuntimeKeyInfo = runtimeKeyInfo;
	indexstate->iss_ScanKeys = scanKeys;
	indexstate->iss_NumScanKeys = numScanKeys;

	/*
	 * If we have runtime keys, we need an ExprContext to evaluate them. The
	 * node's standard context won't do because we want to reset that context
	 * for every tuple.  So, build another context just like the other one...
	 * -tgl 7/11/00
	 */
	if (have_runtime_keys)
	{
		ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;

		ExecAssignExprContext(estate, &indexstate->ss.ps);
		indexstate->iss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
		indexstate->ss.ps.ps_ExprContext = stdecontext;
	}
	else
	{
		indexstate->iss_RuntimeContext = NULL;
	}

	/*
	 * open the base relation and acquire AccessShareLock on it.
	 */
	relid = node->scan.scanrelid;
	rtentry = rt_fetch(relid, estate->es_range_table);
	reloid = rtentry->relid;

	currentRelation = heap_open(reloid, AccessShareLock);

	indexstate->ss.ss_currentRelation = currentRelation;
	indexstate->ss.ss_currentScanDesc = NULL;	/* no heap scan here */

	/*
	 * get the scan type from the relation descriptor.
	 */
	ExecAssignScanType(&indexstate->ss, RelationGetDescr(currentRelation), false);

	/*
	 * open the index relation and initialize relation and scan descriptors.
	 * Note we acquire no locks here; the index machinery does its own locks
	 * and unlocks.  (We rely on having AccessShareLock on the parent table to
	 * ensure the index won't go away!)
	 */
	indexstate->iss_RelationDesc = index_open(node->indexid);
	indexstate->iss_ScanDesc = index_beginscan(currentRelation,
											   indexstate->iss_RelationDesc,
											   estate->es_snapshot,
											   numScanKeys,
											   scanKeys);

	/*
	 * Initialize result tuple type and projection info.
	 */
	ExecAssignResultTypeFromTL(&indexstate->ss.ps);
	ExecAssignScanProjectionInfo(&indexstate->ss);

	/*
	 * all done.
	 */
	return indexstate;
}


/*
 * ExecIndexBuildScanKeys
 *		Build the index scan keys from the index qualification
 *
 * Input params are:
 *
 * planstate: executor state node we are working for
 * quals: indexquals expressions
 * strategies: associated operator strategy numbers
 * subtypes: associated operator subtype OIDs
 *
 * Output params are:
 *
 * *runtimeKeyInfo: receives ptr to array of runtime key exprstates
 *		(NULL if no runtime keys)
 * *scanKeys: receives ptr to array of ScanKeys
 * *numScanKeys: receives number of scankeys/runtime keys
 *
 * Return value is TRUE if any runtime key expressions were found, else FALSE.
 */
bool
ExecIndexBuildScanKeys(PlanState *planstate, List *quals,
					   List *strategies, List *subtypes,
					   ExprState ***runtimeKeyInfo,
					   ScanKey *scanKeys, int *numScanKeys)
{
	bool		have_runtime_keys = false;
	ListCell   *qual_cell;
	ListCell   *strategy_cell;
	ListCell   *subtype_cell;
	int			n_keys;
	ScanKey		scan_keys;
	ExprState **run_keys;
	int			j;

	n_keys = list_length(quals);
	scan_keys = (n_keys <= 0) ? NULL :
		(ScanKey) palloc(n_keys * sizeof(ScanKeyData));
	run_keys = (n_keys <= 0) ? NULL :
		(ExprState **) palloc(n_keys * sizeof(ExprState *));

	/*
	 * for each opclause in the given qual, convert each qual's opclause into
	 * a single scan key
	 */
	qual_cell = list_head(quals);
	strategy_cell = list_head(strategies);
	subtype_cell = list_head(subtypes);

	for (j = 0; j < n_keys; j++)
	{
		OpExpr	   *clause;		/* one clause of index qual */
		Expr	   *leftop;		/* expr on lhs of operator */
		Expr	   *rightop;	/* expr on rhs ... */
		int			flags = 0;
		AttrNumber	varattno;	/* att number used in scan */
		StrategyNumber strategy;	/* op's strategy number */
		Oid			subtype;	/* op's strategy subtype */
		RegProcedure opfuncid;	/* operator proc id used in scan */
		Datum		scanvalue;	/* value used in scan (if const) */

		/*
		 * extract clause information from the qualification
		 */
		clause = (OpExpr *) lfirst(qual_cell);
		qual_cell = lnext(qual_cell);
		strategy = lfirst_int(strategy_cell);
		strategy_cell = lnext(strategy_cell);
		subtype = lfirst_oid(subtype_cell);
		subtype_cell = lnext(subtype_cell);

		if (!IsA(clause, OpExpr))
			elog(ERROR, "indexqual is not an OpExpr");

		opfuncid = clause->opfuncid;

		/*
		 * Here we figure out the contents of the index qual. The usual case
		 * is (var op const) which means we form a scan key for the attribute
		 * listed in the var node and use the value of the const as comparison
		 * data.
		 *
		 * If we don't have a const node, it means our 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 place the appropriate
		 * subexpression in run_keys. The corresponding scan key values are
		 * recomputed at run time.
		 */
		run_keys[j] = NULL;

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

		if (leftop && IsA(leftop, RelabelType))
			leftop = ((RelabelType *) leftop)->arg;

		Assert(leftop != NULL);

		if (!(IsA(leftop, Var) &&
			  var_is_rel((Var *) leftop)))
			elog(ERROR, "indexqual doesn't have key on left side");

		varattno = ((Var *) leftop)->varattno;

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

		if (rightop && IsA(rightop, RelabelType))
			rightop = ((RelabelType *) rightop)->arg;

		Assert(rightop != NULL);

		if (IsA(rightop, Const))
		{
			/*
			 * if the rightop is a const node then it means it identifies the
			 * value to place in our scan key.
			 */
			scanvalue = ((Const *) rightop)->constvalue;
			if (((Const *) rightop)->constisnull)
				flags |= SK_ISNULL;
		}
		else
		{
			/*
			 * otherwise, the rightop contains an expression evaluable at
			 * runtime to figure out the value to place in our scan key.
			 */
			have_runtime_keys = true;
			run_keys[j] = ExecInitExpr(rightop, planstate);
			scanvalue = (Datum) 0;
		}

		/*
		 * initialize the scan key's fields appropriately
		 */
		ScanKeyEntryInitialize(&scan_keys[j],
							   flags,
							   varattno,		/* attribute number to scan */
							   strategy,		/* op's strategy */
							   subtype, /* strategy subtype */
							   opfuncid,		/* reg proc to use */
							   scanvalue);		/* constant */
	}

	/* If no runtime keys, get rid of speculatively-allocated array */
	if (run_keys && !have_runtime_keys)
	{
		pfree(run_keys);
		run_keys = NULL;
	}

	/*
	 * Return the info to our caller.
	 */
	*numScanKeys = n_keys;
	*scanKeys = scan_keys;
	*runtimeKeyInfo = run_keys;

	return have_runtime_keys;
}

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