Support REL_11_STABLE.

get_relid_attribute_name() is gone and is replaced by
get_attname().

ExplainPropertyFloat() requires a new "unit" argument.

Move old-style tuple descriptor usage and access to its attributes
to the "new" TupleDescAttr() macro. We are encouraged to do so since a while.

Since TupleDescAttr() is backpatched to 9.3 and appears first in 9.3.19,
we need to make sure we use the correct definition depending on the
PostgreSQL version we build against.

This makes it important to use a correct build of the informix_fdw.so
library against 9.3 instances.

ifx_fdw.c

@@ -121,6 +121,38 @@ PG_FUNCTION_INFO_V1(ifxCloseConnection);
 #define RTE_UPDATED_COLS(a) (a)->modifiedCols
 #endif
 
+/*
+ * get_relid_attribute_name() is dead as of REL_11_STABLE
+ * (see commit 8237f27b504ff1d1e2da7ae4c81a7f72ea0e0e3e in the
+ * pg repository). Use get_attname() instead. Wrap this into a
+ * compatibility macro, to safe further ifdef's...
+ */
+#if PG_VERSION_NUM >= 110000
+#define pg_attname_by_relid(relid, attnum, missing_ok) \
+	get_attname((relid), (attnum), (missing_ok))
+#else
+#define pg_attname_by_relid(relid, attnum, missing_ok) \
+	get_relid_attribute_name((relid), (attnum))
+#endif
+
+/*
+ * PostgreSQL 9.3 introduced TupleDescrAttr() to access
+ * attributes stored in a tuple descriptor. Use that instead
+ * of directly accessing the tupdesc attribute array, if available.
+ *
+ * CAUTION: This macro was introduced in REL9_3_19 with
+ *          commit 5b286cae3cc1c43d6eedf6cf1181d41f653c6a93,
+ *          so we cannot make it available for all previous
+ *          versions for REL9_3_STABLE.
+ */
+#if PG_VERSION_NUM >= 90319
+#define TUPDESC_GET_ATTR(desc, index) \
+	TupleDescAttr((desc), (index))
+#else
+#define TUPDESC_GET_ATTR(desc, index) \
+	((desc)->attrs[(index)])
+#endif
+
 /*******************************************************************************
  * FDW helper functions.
  */
@@ -1176,7 +1208,7 @@ char *dispatchColumnIdentifier(int varno, int varattno, PlannerInfo *root)
 	 * was found.
 	 */
 	if (ident == NULL)
-		ident = get_relid_attribute_name(rte->relid, varattno);
+		ident = pg_attname_by_relid(rte->relid, varattno, false);
 
 	return ident;
 }
@@ -1889,7 +1921,7 @@ static void ifxPrepareParamsForModify(IfxFdwExecutionState *state,
 			 */
 			for (attnum = 1; attnum <= tupdesc->natts; attnum++)
 			{
-				Form_pg_attribute pgattr = tupdesc->attrs[attnum - 1];
+				Form_pg_attribute pgattr = TUPDESC_GET_ATTR(tupdesc, attnum - 1);
 
 				state->affectedAttrNums = lappend_int(state->affectedAttrNums,
 													  pgattr->attnum);
@@ -5165,7 +5197,11 @@ ifxExplainForeignScan(ForeignScanState *node, ExplainState *es)
 	/* Give some possibly useful info about startup costs */
 	if (es->costs)
 	{
+#if PG_VERSION_NUM >= 110000
+		ExplainPropertyFloat("Informix costs", NULL, planData.costs, 2, es);
+#else
 		ExplainPropertyFloat("Informix costs", planData.costs, 2, es);
+#endif
 
 		/* print planned foreign query */
 		ExplainPropertyText("Informix query", festate->stmt_info.query, es);