Fix nocachegetattr() so it again supports deforming cstrings

c456e3911 added various optimizations to the tuple deformation routines.
One optimization assumed that heap tuples would never contain cstrings.
That optimization also made its way into nocachegetattr(), which isn't
correct as ROW() types get formed into HeapTuples by ExecEvalRow() and
those can contain cstring Datums.  nocachegetattr() gets used to extract
Datums from those tuples.

Here we remove the pg_assume(), which was there to instruct the compiler
to omit the attlen == -2 related code in att_addlength_pointer().

Author: David Rowley <dgrowleyml@gmail.com>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/80aeac57-8f50-4732-a5b4-c2373c3f8149@gmail.com

diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index dce97a162a5e772700d2dfbf3400a0e8945fa049..f30346469ed032592147495be3704f8397d94f81 100644 (file)
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -589,14 +589,6 @@ nocachegetattr(HeapTuple tup,
 
                        cattr = TupleDescCompactAttr(tupleDesc, i);
                        attlen = cattr->attlen;
-
-                       /*
-                        * cstrings don't exist in heap tuples.  Use pg_assume to instruct
-                        * the compiler not to emit the cstring-related code in
-                        * att_addlength_pointer().
-                        */
-                       pg_assume(attlen > 0 || attlen == -1);
-
                        off = att_pointer_alignby(off,
                                                                          cattr->attalignby,
                                                                          attlen,
@@ -613,10 +605,6 @@ nocachegetattr(HeapTuple tup,
 
                        cattr = TupleDescCompactAttr(tupleDesc, i);
                        attlen = cattr->attlen;
-
-                       /* As above, heaptuples have no cstrings */
-                       pg_assume(attlen > 0 || attlen == -1);
-
                        off = att_pointer_alignby(off, cattr->attalignby, attlen,
                                                                          tp + off);
                        off = att_addlength_pointer(off, attlen, tp + off);