Function ExecInitMaterial

src/backend/executor/nodeMaterial.c:219–333

---------------------------------------------------------------- * ExecInitMaterial * ---------------------------------------------------------------- */

 * ----------------------------------------------------------------
 */
MaterialState *
ExecInitMaterial(Material *node, EState *estate, int eflags)
{
	MaterialState *matstate;
	Plan	   *outerPlan;

	/*
	 * create state structure
	 */
	matstate = makeNode(MaterialState);
	matstate->ss.ps.plan = (Plan *) node;
	matstate->ss.ps.state = estate;
	matstate->ss.ps.ExecProcNode = ExecMaterial;

	if (node->cdb_strict)
		eflags |= EXEC_FLAG_REWIND;

	/*
	 * If the Material node was inserted to protect the child node from rescanning, don't
	 * eager free.
	 *
	 * XXX: The planner doesn't always set the flag for Material nodes that are put
	 * directly on top of Motion nodes, so check for that, too. (Or is this for ORCA?)
	 */
	if (node->cdb_shield_child_from_rescans ||
		IsA(outerPlan((Plan *) node), Motion))
	{
		eflags |= EXEC_FLAG_REWIND;
	}

	/*
	 * We must have a tuplestore buffering the subplan output to do backward
	 * scan or mark/restore.  We also prefer to materialize the subplan output
	 * if we might be called on to rewind and replay it many times. However,
	 * if none of these cases apply, we can skip storing the data.
	 */
	matstate->eflags = (eflags & (EXEC_FLAG_REWIND |
								  EXEC_FLAG_BACKWARD |
								  EXEC_FLAG_MARK));

	/*
	 * Tuplestore's interpretation of the flag bits is subtly different from
	 * the general executor meaning: it doesn't think BACKWARD necessarily
	 * means "backwards all the way to start".  If told to support BACKWARD we
	 * must include REWIND in the tuplestore eflags, else tuplestore_trim
	 * might throw away too much.
	 */
	if (eflags & EXEC_FLAG_BACKWARD)
		matstate->eflags |= EXEC_FLAG_REWIND;

	matstate->eof_underlying = false;
	matstate->tuplestorestate = NULL;
	matstate->ts_destroyed = false;

	/*
	 * Miscellaneous initialization
	 *
	 * Materialization nodes don't need ExprContexts because they never call