Function transformIndexConstraints

src/backend/parser/parse_utilcmd.c:3175–3283

* transformIndexConstraints * Handle UNIQUE, PRIMARY KEY, EXCLUDE constraints, which create indexes. * We also merge in any index definitions arising from * LIKE ... INCLUDING INDEXES. */

 *		LIKE ... INCLUDING INDEXES.
 */
static void
transformIndexConstraints(CreateStmtContext *cxt)
{
	IndexStmt  *index;
	List	   *indexlist = NIL;
	List	   *finalindexlist = NIL;
	ListCell   *lc;

	/*
	 * Run through the constraints that need to generate an index. For PRIMARY
	 * KEY, mark each column as NOT NULL and create an index. For UNIQUE or
	 * EXCLUDE, create an index as for PRIMARY KEY, but do not insist on NOT
	 * NULL.
	 */
	foreach(lc, cxt->ixconstraints)
	{
		Constraint *constraint = lfirst_node(Constraint, lc);

		Assert(constraint->contype == CONSTR_PRIMARY ||
			   constraint->contype == CONSTR_UNIQUE ||
			   constraint->contype == CONSTR_EXCLUSION);

		index = transformIndexConstraint(constraint, cxt);

		indexlist = lappend(indexlist, index);
	}

	/*
	 * Scan the index list and remove any redundant index specifications. This
	 * can happen if, for instance, the user writes UNIQUE PRIMARY KEY. A
	 * strict reading of SQL would suggest raising an error instead, but that
	 * strikes me as too anal-retentive. - tgl 2001-02-14
	 *
	 * XXX in ALTER TABLE case, it'd be nice to look for duplicate
	 * pre-existing indexes, too.
	 */
	if (cxt->pkey != NULL)
	{
		/* Make sure we keep the PKEY index in preference to others... */
		finalindexlist = list_make1(cxt->pkey);
	}

	foreach(lc, indexlist)
	{
		bool		keep = true;
		bool		defer = false;
		ListCell   *k;

		index = lfirst(lc);

		/* if it's pkey, it's already in finalindexlist */
		if (index == cxt->pkey)
			continue;

		foreach(k, finalindexlist)
		{
			IndexStmt  *priorindex = lfirst(k);