修复数组计算元素个数整数溢出问题

src/include/utils/array.h

@@ -58,6 +58,13 @@
 
 #include "fmgr.h"
 
+/*
+ * Maximum number of elements in an array. We limit this to at most about a
+ * quarter billion elements, so that it's not necessary to check for overflow
+ * in quite so many places --- for instance when polloc'ing Datum arrays.
+ */
+#define MaxArraySize ((Size)(MaxAllocSize) / sizeof(Datum))
+
 /*
  * Arrays are varlena objects, so must meet the varlena convention that
  * the first int32 of the object contains the total object size in bytes.