Function ExecInitSampleScan

src/backend/executor/nodeSamplescan.c:95–173

---------------------------------------------------------------- * ExecInitSampleScan * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
SampleScanState *
ExecInitSampleScan(SampleScan *node, EState *estate, int eflags)
{
	SampleScanState *scanstate;
	TableSampleClause *tsc = node->tablesample;
	TsmRoutine *tsm;

	Assert(outerPlan(node) == NULL);
	Assert(innerPlan(node) == NULL);

	/*
	 * create state structure
	 */
	scanstate = makeNode(SampleScanState);
	scanstate->ss.ps.plan = (Plan *) node;
	scanstate->ss.ps.state = estate;
	scanstate->ss.ps.ExecProcNode = ExecSampleScan;

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

	/*
	 * open the scan relation
	 */
	scanstate->ss.ss_currentRelation =
		ExecOpenScanRelation(estate,
							 node->scan.scanrelid,
							 eflags);

	/* we won't set up the HeapScanDesc till later */
	scanstate->ss.ss_currentScanDesc = NULL;

	/* and create slot with appropriate rowtype */
	ExecInitScanTupleSlot(estate, &scanstate->ss,
						  RelationGetDescr(scanstate->ss.ss_currentRelation),
						  table_slot_callbacks(scanstate->ss.ss_currentRelation));

	/*
	 * Initialize result type and projection.
	 */
	ExecInitResultTypeTL(&scanstate->ss.ps);
	ExecAssignScanProjectionInfo(&scanstate->ss);

	/*
	 * initialize child expressions
	 */
	scanstate->ss.ps.qual =
		ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);

	scanstate->args = ExecInitExprList(tsc->args, (PlanState *) scanstate);
	scanstate->repeatable =
		ExecInitExpr(tsc->repeatable, (PlanState *) scanstate);

	/*