Thread

1. BUG #19020: BufFileDumpBuffer writes uninitialized data on executing hash join

   PG Bug reporting form <noreply@postgresql.org> — 2025-08-16T12:00:01Z

   The following bug has been logged on the website:
   
   Bug reference:      19020
   Logged by:          Alexander Lakhin
   Email address:      exclusion@gmail.com
   PostgreSQL version: 18beta3
   Operating system:   Ubuntu 24.04
   Description:        
   
   The following script, when executed under Valgrind:
   CREATE TABLE tenk1 (
                   unique1         int4,
                   unique2         int4,
                   two                     int4,
                   stud_emp                int4,
                   ten                     int4,
                   twenty          int4,
                   hundred         int4,
                   thousand        int4,
                   twothousand     int4,
                   fivethous       int4,
                   tenthous        int4,
                   odd                     int4,
                   even            int4,
                   stringu1        name,
                   stringu2        name,
                   string4         name
           );
   
   COPY tenk1 FROM '.../src/test/regress/data/tenk.data';
   VACUUM ANALYZE tenk1;
   
   SET work_mem = '64kB';
   SELECT COUNT(*) FROM tenk1 JOIN generate_series(1, 1300) g ON unique1 = g;
   
   triggers an error:
   ==00:00:00:06.424 2914013== Syscall param pwrite64(buf) points to
   uninitialised byte(s)
   ==00:00:00:06.424 2914013==    at 0x4FF8517: pwrite (pwrite64.c:25)
   ==00:00:00:06.424 2914013==    by 0x7C10E8: pg_pwritev (pg_iovec.h:101)
   ==00:00:00:06.424 2914013==    by 0x7C3BD1: FileWriteV (fd.c:2293)
   ==00:00:00:06.424 2914013==    by 0x7BEB0A: FileWrite (fd.h:219)
   ==00:00:00:06.424 2914013==    by 0x7BF685: BufFileDumpBuffer
   (buffile.c:538)
   ==00:00:00:06.424 2914013==    by 0x7BFC6A: BufFileFlush (buffile.c:724)
   ==00:00:00:06.424 2914013==    by 0x7BF841: BufFileReadCommon
   (buffile.c:600)
   ==00:00:00:06.424 2914013==    by 0x7BFACD: BufFileReadMaybeEOF
   (buffile.c:667)
   ==00:00:00:06.424 2914013==    by 0x54FC94: ExecHashJoinGetSavedTuple
   (nodeHashjoin.c:1476)
   ==00:00:00:06.424 2914013==    by 0x54F140: ExecHashJoinOuterGetTuple
   (nodeHashjoin.c:1042)
   ==00:00:00:06.424 2914013==    by 0x54E139: ExecHashJoinImpl
   (nodeHashjoin.c:432)
   ==00:00:00:06.424 2914013==    by 0x54E7D2: ExecHashJoin
   (nodeHashjoin.c:690)
   ==00:00:00:06.424 2914013==  Address 0x11dc8a88 is 80 bytes inside a block
   of size 8,264 client-defined
   ==00:00:00:06.424 2914013==    at 0xA651F2: palloc (mcxt.c:1389)
   ==00:00:00:06.424 2914013==    by 0x7BEB39: makeBufFileCommon
   (buffile.c:120)
   ==00:00:00:06.424 2914013==    by 0x7BEBB1: makeBufFile (buffile.c:141)
   ==00:00:00:06.424 2914013==    by 0x7BED3C: BufFileCreateTemp
   (buffile.c:212)
   ==00:00:00:06.424 2914013==    by 0x54FBE6: ExecHashJoinSaveTuple
   (nodeHashjoin.c:1437)
   ==00:00:00:06.424 2914013==    by 0x54E309: ExecHashJoinImpl
   (nodeHashjoin.c:494)
   ==00:00:00:06.424 2914013==    by 0x54E7D2: ExecHashJoin
   (nodeHashjoin.c:690)
   ==00:00:00:06.424 2914013==    by 0x521ED9: ExecProcNodeFirst
   (execProcnode.c:469)
   ==00:00:00:06.424 2914013==    by 0x533ADB: ExecProcNode (executor.h:315)
   ==00:00:00:06.424 2914013==    by 0x5340B1: fetch_input_tuple
   (nodeAgg.c:563)
   ==00:00:00:06.424 2914013==    by 0x5377C9: agg_retrieve_direct
   (nodeAgg.c:2450)
   ==00:00:00:06.424 2914013==    by 0x537399: ExecAgg (nodeAgg.c:2265)
   ==00:00:00:06.424 2914013==
   ...
   ==00:00:00:06.496 2915423== Exit program on first error
   (--exit-on-first-error=yes)
   2025-08-16 11:28:47.537 UTC [2915382] LOG:  client backend (PID 2915423)
   exited with exit code 1
   2025-08-16 11:28:47.537 UTC [2915382] DETAIL:  Failed process was running:
   SELECT COUNT(*) FROM tenk1 JOIN generate_series(1, 1300) g ON unique1 = g;
   
   Reproduced on REL_13_STABLE .. master.
   
   

2. Re: BUG #19020: BufFileDumpBuffer writes uninitialized data on executing hash join

   Tom Lane <tgl@sss.pgh.pa.us> — 2025-08-16T14:11:24Z

   PG Bug reporting form <noreply@postgresql.org> writes:
   > ==00:00:00:06.424 2914013== Syscall param pwrite64(buf) points to
   > uninitialised byte(s)
   > ==00:00:00:06.424 2914013==    at 0x4FF8517: pwrite (pwrite64.c:25)
   > ==00:00:00:06.424 2914013==    by 0x7C10E8: pg_pwritev (pg_iovec.h:101)
   > ==00:00:00:06.424 2914013==    by 0x7C3BD1: FileWriteV (fd.c:2293)
   > ==00:00:00:06.424 2914013==    by 0x7BEB0A: FileWrite (fd.h:219)
   > ==00:00:00:06.424 2914013==    by 0x7BF685: BufFileDumpBuffer
   > (buffile.c:538)
   
   Looks like this path needs to be added to the suppressions in
   src/tools/valgrind.supp.  I'm a bit surprised that the buildfarm
   hasn't already shown this up.
   
   			regards, tom lane