Server crashed with "TRAP: unrecognized TOAST vartag("1", File:"heaptuple.c", Line: 1490)"

postgres=# CREATE TABLE part_tbl (a INT, b TEXT, c INT) PARTITION BY RANGE(a);
CREATE TABLE
postgres=# CREATE TABLE part_tbl_p PARTITION OF part_tbl FOR VALUES FROM (minvalue) TO (maxvalue);
CREATE TABLE
postgres=# CREATE INDEX partidx_abc_idx ON part_tbl (a, b, c);
CREATE INDEX
postgres=# INSERT INTO part_tbl (a, b, c) SELECT i,i,i FROM generate_series(1,50)i;
INSERT 0 50
postgres=# ANALYZE part_tbl;
ANALYZE
postgres=# ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;
server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!>


--logfile
TRAP: unrecognized TOAST vartag("1", File: "heaptuple.c", Line: 1490)
2018-06-28 00:01:01.679 IST [97062] LOG:  server process (PID 97080) was terminated by signal 6: Aborted
2018-06-28 00:01:01.679 IST [97062] DETAIL:  Failed process was running: ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;

--corefile
Core was generated by `postgres: edb postgres [local] ALTER TABLE              '.
Program terminated with signal 6, Aborted.
#0  0x0000003dd2632495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
64      return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
Missing separate debuginfos, use: debuginfo-install keyutils-libs-1.4-5.el6.x86_64 krb5-libs-1.10.3-65.el6.x86_64 libcom_err-1.41.12-23.el6.x86_64 libselinux-2.0.94-7.el6.x86_64 openssl-1.0.1e-57.el6.x86_64 zlib-1.2.3-29.el6.x86_64
(gdb) bt
#0  0x0000003dd2632495 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x0000003dd2633c75 in abort () at abort.c:92
#2  0x0000000000a337ee in ExceptionalCondition (conditionName=0xaa3290 "1", errorType=0xaa3276 "unrecognized TOAST vartag", fileName=0xaa31e0 "heaptuple.c", lineNumber=1490)
    at assert.c:54
#3  0x0000000000487c9c in slot_deform_tuple (slot=0x1fa2d68, natts=3) at heaptuple.c:1490
#4  0x0000000000487fc2 in slot_getattr (slot=0x1fa2d68, attnum=3, isnull=0x7ffea43368e7) at heaptuple.c:1595
#5  0x000000000057b10d in FormIndexDatum (indexInfo=0x1f91138, slot=0x1fa2d68, estate=0x1f95c98, values=0x7ffea4336be0, isnull=0x7ffea4336bc0) at index.c:2032
#6  0x000000000057c459 in IndexBuildHeapRangeScan (heapRelation=0x7f3944067c40, indexRelation=0x7f3944067a28, indexInfo=0x1f91138, allow_sync=true, anyvisible=false,
    start_blockno=0, numblocks=4294967295, callback=0x5123ab <_bt_build_callback>, callback_state=0x7ffea4336ea0, scan=0x1f91b80) at index.c:2876
#7  0x000000000057bac1 in IndexBuildHeapScan (heapRelation=0x7f3944067c40, indexRelation=0x7f3944067a28, indexInfo=0x1f91138, allow_sync=true,
    callback=0x5123ab <_bt_build_callback>, callback_state=0x7ffea4336ea0, scan=0x0) at index.c:2426
#8  0x0000000000512222 in _bt_spools_heapscan (heap=0x7f3944067c40, index=0x7f3944067a28, buildstate=0x7ffea4336ea0, indexInfo=0x1f91138) at nbtsort.c:472
#9  0x0000000000511f72 in btbuild (heap=0x7f3944067c40, index=0x7f3944067a28, indexInfo=0x1f91138) at nbtsort.c:324
#10 0x000000000057b6fb in index_build (heapRelation=0x7f3944067c40, indexRelation=0x7f3944067a28, indexInfo=0x1f91138, isprimary=false, isreindex=false, parallel=true)
    at index.c:2288
#11 0x0000000000579d49 in index_create (heapRelation=0x7f3944067c40, indexRelationName=0x1f9b370 "part_tbl_p_a_b_c_idx", indexRelationId=16396, parentIndexRelid=16395,
    parentConstraintId=0, relFileNode=0, indexInfo=0x1f91138, indexColNames=0x1f9b288, accessMethodObjectId=403, tableSpaceId=1663, collationObjectId=0x1f9b460,
    classObjectId=0x1f9b488, coloptions=0x1f9b4b0, reloptions=0, flags=0, constr_flags=0, allow_system_table_mods=false, is_internal=true, constraintId=0x7ffea433715c)
    at index.c:1187
#12 0x000000000066488d in DefineIndex (relationId=16387, stmt=0x1f90eb8, indexRelationId=0, parentIndexId=16395, parentConstraintId=0, is_alter_table=true, check_rights=false,
    check_not_in_use=false, skip_build=false, quiet=true) at indexcmds.c:850
#13 0x0000000000664e7f in DefineIndex (relationId=16384, stmt=0x1f79688, indexRelationId=16395, parentIndexId=0, parentConstraintId=0, is_alter_table=true, check_rights=false,
    check_not_in_use=false, skip_build=true, quiet=true) at indexcmds.c:1031
#14 0x000000000068ff68 in ATExecAddIndex (tab=0x1f744f8, rel=0x7f3944061b50, stmt=0x1f79688, is_rebuild=true, lockmode=8) at tablecmds.c:6958
#15 0x000000000068977f in ATExecCmd (wqueue=0x7ffea4337838, tab=0x1f744f8, rel=0x7f3944061b50, cmd=0x1f90e60, lockmode=8) at tablecmds.c:4090
#16 0x00000000006891a9 in ATRewriteCatalogs (wqueue=0x7ffea4337838, lockmode=8) at tablecmds.c:3989
#17 0x0000000000688880 in ATController (parsetree=0x1f81460, rel=0x7f3944061b50, cmds=0x1f74460, recurse=true, lockmode=8) at tablecmds.c:3639
#18 0x00000000006885a9 in AlterTable (relid=16384, lockmode=8, stmt=0x1f81460) at tablecmds.c:3312
#19 0x00000000008cea8e in ProcessUtilitySlow (pstate=0x1f81348, pstmt=0x1eb95a0, queryString=0x1eb8798 "ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;",
    context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x1eb9890, completionTag=0x7ffea4337fd0 "") at utility.c:1117
#20 0x00000000008ce50e in standard_ProcessUtility (pstmt=0x1eb95a0, queryString=0x1eb8798 "ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;",
    context=PROCESS_UTILITY_TOPLEVEL, params=0x0, queryEnv=0x0, dest=0x1eb9890, completionTag=0x7ffea4337fd0 "") at utility.c:920
#21 0x00000000008cd530 in ProcessUtility (pstmt=0x1eb95a0, queryString=0x1eb8798 "ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;", context=PROCESS_UTILITY_TOPLEVEL,
    params=0x0, queryEnv=0x0, dest=0x1eb9890, completionTag=0x7ffea4337fd0 "") at utility.c:360
#22 0x00000000008cc4de in PortalRunUtility (portal=0x1f1dc28, pstmt=0x1eb95a0, isTopLevel=true, setHoldSnapshot=false, dest=0x1eb9890, completionTag=0x7ffea4337fd0 "")
    at pquery.c:1178
#23 0x00000000008cc706 in PortalRunMulti (portal=0x1f1dc28, isTopLevel=true, setHoldSnapshot=false, dest=0x1eb9890, altdest=0x1eb9890, completionTag=0x7ffea4337fd0 "")
    at pquery.c:1324
#24 0x00000000008cbbf3 in PortalRun (portal=0x1f1dc28, count=9223372036854775807, isTopLevel=true, run_once=true, dest=0x1eb9890, altdest=0x1eb9890,
    completionTag=0x7ffea4337fd0 "") at pquery.c:799
#25 0x00000000008c5afc in exec_simple_query (query_string=0x1eb8798 "ALTER TABLE part_tbl ALTER COLUMN c TYPE numeric;") at postgres.c:1122
#26 0x00000000008c9dd2 in PostgresMain (argc=1, argv=0x1ee22a0, dbname=0x1ee2100 "postgres", username=0x1eb5298 "edb") at postgres.c:4153
#27 0x0000000000827467 in BackendRun (port=0x1eda060) at postmaster.c:4361