Function create_plan

src/backend/optimizer/plan/createplan.c:379–441

* create_plan * Creates the access plan for a query by recursively processing the * desired tree of pathnodes, starting at the node 'best_path'. For * every pathnode found, we create a corresponding plan node containing * appropriate id, target list, and qualification information. * * The tlists and quals in the plan tree are still in planner format, * ie, Vars still correspond

 *	  Returns a Plan tree.
 */
Plan *
create_plan(PlannerInfo *root, Path *best_path, PlanSlice *curSlice)
{
	Plan	   *plan;

	root->curSlice = curSlice;

	/* plan_params should not be in use in current query level */
	Assert(root->plan_params == NIL);

	/* Initialize this module's workspace in PlannerInfo */
	root->curOuterRels = NULL;
	root->curOuterParams = NIL;

	/* Recursively process the path tree, demanding the correct tlist result */
	plan = create_plan_recurse(root, best_path, CP_EXACT_TLIST);

	/*
	 * 'partition_selector_candidates' is a stack, should be empty now
	 * that we're back from create_plan_recurse().
	 */
	Assert(root->partition_selector_candidates == NIL);

	/*
	 * Make sure the topmost plan node's targetlist exposes the original
	 * column names and other decorative info.  Targetlists generated within
	 * the planner don't bother with that stuff, but we must have it on the
	 * top-level tlist seen at execution time.  However, ModifyTable plan
	 * nodes don't have a tlist matching the querytree targetlist.
	 *
	 * The ModifyTable might be under a Motion, so peek underneath it.
	 */
	{
		Plan	   *topplan = plan;

		if (IsA(plan, Motion))
			topplan = plan->lefttree;

		if (!IsA(topplan, ModifyTable))
			apply_tlist_labeling(topplan->targetlist, root->processed_tlist);
	}

	/*
	 * Attach any initPlans created in this query level to the topmost plan
	 * node.  (In principle the initplans could go in any plan node at or
	 * above where they're referenced, but there seems no reason to put them
	 * any lower than the topmost node for the query level.  Also, see
	 * comments for SS_finalize_plan before you try to change this.)
	 */
	SS_attach_initplans(root, plan);

	/* Check we successfully assigned all NestLoopParams to plan nodes */
	if (root->curOuterParams != NIL)
		elog(ERROR, "failed to assign all NestLoopParams to plan nodes");

	/*
	 * Reset plan_params to ensure param IDs used for nestloop params are not
	 * re-used later