Function transformSetOperationTree

src/backend/parser/analyze.c:2091–2125

* transformSetOperationTree * Recursively transform leaves and internal nodes of a set-op tree * * In addition to returning the transformed node, if targetlist isn't NULL * then we return a list of its non-resjunk TargetEntry nodes. For a leaf * set-op node these are the actual targetlist entries; otherwise they are * dummy entries created to carry the type, typmod, collation, and location

 * replace UNKNOWN Consts with properly-coerced constants.
 */
static Node *
transformSetOperationTree(ParseState *pstate, SelectStmt *stmt,
						  bool isTopLevel, List **targetlist)
{
	setop_types_ctx ctx;
	Node	   *top;
	List	   *selected_types;
	List	   *selected_typmods;

	/*
	 * Transform all the subtrees.
	 */
	ctx.ncols = -1;
	ctx.leafinfos = NULL;
	top = transformSetOperationTree_internal(pstate, stmt, isTopLevel, &ctx);
	Assert(ctx.ncols >= 0);

	/*
	 * We have now transformed all the subtrees, and collected all the
	 * data types and typmods of the columns from each leaf node.
	 *
	 * In PostgreSQL, we also choose the result type for each subtree as we
	 * recurse, but in GPDB, we do that here as a separate pass. That way, we
	 * have can make the decision globally based on every leaf, rather
	 * separately for each subtree.
	 *
	 * There are also some hacks to more leniently coerce between types, to
	 * make some cases not error out.
	 */
	select_setop_types(pstate, &ctx, stmt->op, &selected_types, &selected_typmods);

	coerceSetOpTypes(pstate, top, selected_types, selected_typmods, targetlist);

	return top;
}

static void
select_setop_types(ParseState *pstate, setop_types_ctx *ctx, SetOperation op, List **selected_types, List **selected_typmods)