Function ExecInitLimit

src/backend/executor/nodeLimit.c:471–551

---------------------------------------------------------------- * ExecInitLimit * * This initializes the limit node state structures and * the node's subplan. * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
LimitState *
ExecInitLimit(Limit *node, EState *estate, int eflags)
{
	LimitState *limitstate;
	Plan	   *outerPlan;

	/* check for unsupported flags */
	Assert(!(eflags & EXEC_FLAG_MARK));

	/*
	 * create state structure
	 */
	limitstate = makeNode(LimitState);
	limitstate->ps.plan = (Plan *) node;
	limitstate->ps.state = estate;
	limitstate->ps.ExecProcNode = ExecLimit;

	limitstate->lstate = LIMIT_INITIAL;

	/*
	 * Miscellaneous initialization
	 *
	 * Limit nodes never call ExecQual or ExecProject, but they need an
	 * exprcontext anyway to evaluate the limit/offset parameters in.
	 */
	ExecAssignExprContext(estate, &limitstate->ps);

	/*
	 * initialize outer plan
	 */
	outerPlan = outerPlan(node);
	outerPlanState(limitstate) = ExecInitNode(outerPlan, estate, eflags);

	/*
	 * initialize child expressions
	 */
	limitstate->limitOffset = ExecInitExpr((Expr *) node->limitOffset,
										   (PlanState *) limitstate);
	limitstate->limitCount = ExecInitExpr((Expr *) node->limitCount,
										  (PlanState *) limitstate);
	limitstate->limitOption = node->limitOption;

	/*
	 * Initialize result type.
	 */
	ExecInitResultTypeTL(&limitstate->ps);

	limitstate->ps.resultopsset = true;
	limitstate->ps.resultops = ExecGetResultSlotOps(outerPlanState(limitstate),
													&limitstate->ps.resultopsfixed);

	/*
	 * limit nodes do no projections, so initialize projection info for this
	 * node appropriately
	 */
	limitstate->ps.ps_ProjInfo = NULL;

	limitstate->expect_rescan = ((eflags & EXEC_FLAG_REWIND) != 0);