Function ExecInitGroup

src/backend/executor/nodeGroup.c:161–219

----------------- * ExecInitGroup * * Creates the run-time information for the group node produced by the * planner and initializes its outer subtree * ----------------- */

 * -----------------
 */
GroupState *
ExecInitGroup(Group *node, EState *estate, int eflags)
{
	GroupState *grpstate;
	const TupleTableSlotOps *tts_ops;

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

	/*
	 * create state structure
	 */
	grpstate = makeNode(GroupState);
	grpstate->ss.ps.plan = (Plan *) node;
	grpstate->ss.ps.state = estate;
	grpstate->ss.ps.ExecProcNode = ExecGroup;
	grpstate->grp_done = false;

	/*
	 * create expression context
	 */
	ExecAssignExprContext(estate, &grpstate->ss.ps);

	/*
	 * initialize child nodes
	 */
	outerPlanState(grpstate) = ExecInitNode(outerPlan(node), estate, eflags);

	/*
	 * Initialize scan slot and type.
	 */
	tts_ops = ExecGetResultSlotOps(outerPlanState(&grpstate->ss), NULL);
	ExecCreateScanSlotFromOuterPlan(estate, &grpstate->ss, tts_ops);

	/*
	 * Initialize result slot, type and projection.
	 */
	ExecInitResultTupleSlotTL(&grpstate->ss.ps, &TTSOpsVirtual);
	ExecAssignProjectionInfo(&grpstate->ss.ps, NULL);

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

	/*
	 * Precompute fmgr lookup data for inner loop
	 */
	grpstate->eqfunction =
		execTuplesMatchPrepare(ExecGetResultType(outerPlanState(grpstate)),
							   node->numCols,
							   node->grpColIdx,
							   node->grpOperators,
							   node->grpCollations,
							   &grpstate->ss.ps);

	return grpstate;