MIME-Version: 1.0
Date: Thu, 23 Oct 2025 12:47:13 +0300
From: Oleg Tselebrovskiy <o.tselebrovskiy@postgrespro.ru>
To: pgsql-hackers@postgresql.org
Subject: 001_password.pl fails with --without-readline
Message-ID: <db6fdb35a8665ad3c18be01181d44b31@postgrespro.ru>
Organization: Postgres Pro
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Greetings!

If you configure PostgreSQL with --without-readline, test 
authentication/t/001_password.pl fails due to timeout

This can be reproduced on any branch that contains commit 8b886a4 (so, 
on PostgreSQL 13-19)

I've looked through debug info using IPCRUNDEBUG = "data" or "details"

Here's some output:

This is with readline:
     [18:31:45.030](0.027s) ok 22 - scram_iterations in server side ROLE
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: write( 10, '\echo background_psql: 
ready
     IPC::Run 0001 [#15(253566)]: \warn background_psql: ready
     IPC::Run 0001 [#15(253566)]: ' ) = 58
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: read( 10 ) = 60 chars '\echo 
background_psql: ready
     IPC::Run 0001 [#15(253566)]: \warn background_psql: ready
     IPC::Run 0001 [#15(253566)]: '
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: read( 10 ) = 41 chars 'psql (19devel)
     IPC::Run 0001 [#15(253566)]: Type "help" for help.
     IPC::Run 0001 [#15(253566)]:
     IPC::Run 0001 [#15(253566)]: '
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: read( 10 ) = 11 chars 'postgres=# '
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: read( 10 ) = 65 chars '\echo 
background_psql: ready
     IPC::Run 0001 [#15(253566)]: background_psql: ready
     IPC::Run 0001 [#15(253566)]: postgres=# '
     IPC::Run 0001 [#15(253566)]: ** pumping
     IPC::Run 0001 [#15(253566)]: read( 10 ) = 41 chars '\warn 
background_psql: ready
     IPC::Run 0001 [#15(253566)]: postgres=# '
     IPC::Run 0001 [#15(253566)]: read( 12 ) = 23 chars 'background_psql: 
ready
     IPC::Run 0001 [#15(253566)]: '
     [18:31:45.042](0.013s) # connect output:

And this is without readline:
     [18:34:32.050](0.029s) ok 22 - scram_iterations in server side ROLE
     IPC::Run 0001 [#15(263802)]: ** pumping
     IPC::Run 0001 [#15(263802)]: write( 10, '\echo background_psql: 
ready
     IPC::Run 0001 [#15(263802)]: \warn background_psql: ready
     IPC::Run 0001 [#15(263802)]: ' ) = 58
     IPC::Run 0001 [#15(263802)]: ** pumping
     IPC::Run 0001 [#15(263802)]: read( 10 ) = 60 chars '\echo 
background_psql: ready
     IPC::Run 0001 [#15(263802)]: \warn background_psql: ready
     IPC::Run 0001 [#15(263802)]: '
     IPC::Run 0001 [#15(263802)]: ** pumping
     IPC::Run 0001 [#15(263802)]: read( 10 ) = 98 chars 'psql (19devel)
     IPC::Run 0001 [#15(263802)]: Type "help" for help.
     IPC::Run 0001 [#15(263802)]:
     IPC::Run 0001 [#15(263802)]: postgres=# background_psql: ready
     IPC::Run 0001 [#15(263802)]: postgres=# postgres=# '
     IPC::Run 0001 [#15(263802)]: ** pumping
     IPC::Run 0001 [#15(263802)]: read( 12 ) = 23 chars 'background_psql: 
ready
     IPC::Run 0001 [#15(263802)]: '
     IPC::Run 0001 [#15(263802)]: ** pumping

As you can see, those outputs are different

1) In readline output commands \echo and \warn are re-read (that's why 
banner_match in BackgroundPsql.pm has checks for \n or start of line), 
but in no-readline output both \echo and \warn are read only once, when 
they are first send to psql

2) In readline ouput stdout is re-read multiple times, and banner 
(background_psql: ready) is placed neatly on it's own line, while in 
no-readline output banner in stdout is mixed with "postgres=#" prompts, 
and they are read as one batch

Those differences are probably an effect of inner workings of readline, 
turning input echoing off.

Also, without readline, stdout during query exectution can look like 
this
     # \\echo background_psql: QUERY_SEPARATOR 1:
     # \\warn background_psql: QUERY_SEPARATOR 1:
     # SET
     # postgres=# postgres=# background_psql: QUERY_SEPARATOR 1:
     # postgres=# '

So, there are some ways to handle this situation

1) Skip this test if Postgres is configured without readline support. I 
don't think this is a good way, since this test doesn't really test 
anything that needs readline to work

2) Modify variable banner_match depending on having readline or not. 
Something like the attached

I'm interested to hear your thoughts on this

Oleg Tselebrovskiy, PostgresPro

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