Horton

Re: Relations being opened without any lock whatever

Amit Langote <langote_amit_f8@lab.ntt.co.jp>

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From: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@lists.postgresql.org
Date: 2018-10-01T07:19:58Z
Lists: pgsql-hackers 
On 2018/10/01 4:20, Tom Lane wrote:
> Running the regression tests with the patch I showed in
> https://www.postgresql.org/message-id/16565.1538327894@sss.pgh.pa.us
> exposes two places where HEAD is opening relations without having
> any lock at all on them:

Maybe you've noticed but the relation_open calls coming from bootstrap.c
all pass NoLock which trigger the WARNING:

$ initdb -D /tmp/foo
<snip>
WARNING:  relation_open: no lock held on pg_type
WARNING:  relation_open: no lock held on pg_attrdef
WARNING:  relation_open: no lock held on pg_constraint
WARNING:  relation_open: no lock held on pg_inherits
WARNING:  relation_open: no lock held on pg_index
WARNING:  relation_open: no lock held on pg_operator
WARNING:  relation_open: no lock held on pg_opfamily
<so on>

Do we need to do something about that, like teaching boot_openrel() and
gettype() in bootstrap.c to pass AccessShareLock instead of NoLock?

Thanks,
Amit

Commits

  1. Fix tuple_data_split() to not open a relation without any lock.

  2. Lock relation used to generate fresh data for RMV.

  3. Fix ALTER COLUMN TYPE to not open a relation without any lock.