Function transformIndexStmt

src/backend/parser/parse_utilcmd.c:3944–4030

* transformIndexStmt - parse analysis for CREATE INDEX and ALTER TABLE * * Note: this is a no-op for an index not using either index expressions or * a predicate expression. There are several code paths that create indexes * without bothering to call this, because they know they don't have any * such expressions to deal with. * * To avoid race conditions, it's important that this function

 * relation.
 */
IndexStmt *
transformIndexStmt(Oid relid, IndexStmt *stmt, const char *queryString)
{
	ParseState *pstate;
	ParseNamespaceItem *nsitem;
	ListCell   *l;
	Relation	rel;

	/* Nothing to do if statement already transformed. */
	if (stmt->transformed)
		return stmt;

	/* Set up pstate */
	pstate = make_parsestate(NULL);
	pstate->p_sourcetext = queryString;

	/*
	 * Put the parent table into the rtable so that the expressions can refer
	 * to its fields without qualification.  Caller is responsible for locking
	 * relation, but we still need to open it.
	 */
	rel = relation_open(relid, NoLock);
	nsitem = addRangeTableEntryForRelation(pstate, rel,
										   AccessShareLock,
										   NULL, false, true);

	/* no to join list, yes to namespaces */
	addNSItemToQuery(pstate, nsitem, false, true, true);

	/* take care of the where clause */
	if (stmt->whereClause)
	{
		stmt->whereClause = transformWhereClause(pstate,
												 stmt->whereClause,
												 EXPR_KIND_INDEX_PREDICATE,
												 "WHERE");
		/* we have to fix its collations too */
		assign_expr_collations(pstate, stmt->whereClause);
	}

	/* take care of any index expressions */
	foreach(l, stmt->indexParams)
	{
		IndexElem  *ielem = (IndexElem *) lfirst(l);

		if (ielem->expr)
		{
			/* Extract preliminary index col name before transforming expr */
			if (ielem->indexcolname == NULL)
				ielem->indexcolname = FigureIndexColname(ielem->expr);

			/* Now do parse transformation of the expression */
			ielem->expr = transformExpr(pstate, ielem->expr,
										EXPR_KIND_INDEX_EXPRESSION);

			/* We have to fix its collations too */
			assign_expr_collations(pstate, ielem->expr);