Function ExecInitNode

src/backend/executor/execProcnode.c:189–570

------------------------------------------------------------------------ * ExecInitNode * * Recursively initializes all the nodes in the plan tree rooted * at 'node'. * * Inputs: * 'node' is the current node of the plan produced by the query planner * 'estate' is the shared execution state for the plan tree * 'eflags' is a bitwise OR of flag bits described in executor.h * *

 * ------------------------------------------------------------------------
 */
PlanState *
ExecInitNode(Plan *node, EState *estate, int eflags)
{
	PlanState  *result;
	List	   *subps;
	ListCell   *l;
	MemoryContext nodecxt = NULL;
	MemoryContext oldcxt = NULL;

	/*
	 * do nothing when we get to the end of a leaf on tree.
	 */
	if (node == NULL)
		return NULL;

	/*
	 * Make sure there's enough stack available. Need to check here, in
	 * addition to ExecProcNode() (via ExecProcNodeFirst()), to ensure the
	 * stack isn't overrun while initializing the node tree.
	 */
	check_stack_depth();

	/*
	 * If per-node memory usage was requested
	 * (explain_memory_verbosity=detail), create a separate memory context
	 * for every node, so that we can attribute memory usage to each node.
	 * Otherwise, everything is allocated in the per-query ExecutorState
	 * context. The extra memory contexts consume some memory on their
	 * own, and prevent reusing memory allocated in one node in another
	 * node, so we only want to do this if the level of detail is needed.
	 */
	if ((estate->es_instrument & INSTRUMENT_MEMORY_DETAIL) != 0)
	{
		nodecxt = AllocSetContextCreate(CurrentMemoryContext,
										"executor node",
										ALLOCSET_SMALL_SIZES);
		MemoryContextDeclareAccountingRoot(nodecxt);
		oldcxt = MemoryContextSwitchTo(nodecxt);
	}

	switch (nodeTag(node))
	{
			/*
			 * control nodes
			 */
		case T_Result:
			result = (PlanState *) ExecInitResult((Result *) node,
												  estate, eflags);
			break;

		case T_ProjectSet:
			result = (PlanState *) ExecInitProjectSet((ProjectSet *) node,
													  estate, eflags);
			break;

		case T_ModifyTable:
			result = (PlanState *) ExecInitModifyTable((ModifyTable *) node,
													   estate, eflags);