Re: Improvements in psql hooks for variables

Stephen Frost wrote:

> Are you working to make those changes? I'd rather we make the changes
> to this code once rather than push what you have now only to turn around
> and change it significantly again.

So I went through the psql commands which don't fail on parse errors
for booleans. I'd like to attract attention on \c, because I see
several options.

\c [-reuse-previous=BOOL] ...other args..

Current: if we can't parse BOOL, assume it's ON, and go on with reconnecting.

Option1: if we can't parse BOOL, stop here, don't reconnect, set
the command result as "failed", also ignoring the other arguments.

Option2: maybe we want to create a difference between interactive
and non-interactive use, as there's already one in handling
the failure to connect through \c.
The manpage says:
If the connection attempt failed (wrong user name, access denied,
etc.), the previous connection will only be kept if psql is in
interactive mode. When executing a non-interactive script,
processing will immediately stop with an error.

Proposal: if interactive, same as Option1.
If not interactive, -reuse-previous=bogus has the same outcome
as a failure to connect. Which I think means two subcases:
if it's through \i then kill the connection but don't quit psql
if it's through -f then quit psql.

Option3: leave this command unchanged, avoiding trouble.

\timing BOOL

Current: non-parseable BOOL interpreted as TRUE. Empty BOOL toggles the
state.

Proposal: on non-parseable BOOL, command failure and pset.timing is
left unchanged.

\pset [x | expanded | vertical ] BOOL
\pset numericlocale BOOL
\pset [tuples_only | t] BOOL
\pset footer BOOL
\t BOOL (falls into pset_do("tuples_only", ...))
\pset pager BOOL

Current: non-parseable non-empty BOOL interpreted as TRUE. Empty BOOL
toggles the on/off state. In some cases, BOOL interpretation is attempted
only after specific built-in values have been ruled out first.

Proposal: non-parseable BOOL implies command failure and unchanged state.

About the empty string when a BOOL is expected. Only \c -reuse-previous
seems concerned:

#= \c -reuse-previous=
acts the same as
#= \c -reuse-previous=ON

Proposal: handle empty as when the value is bogus.

The other commands interpret this lack of value specifically to toggle
the state, so it's a non-issue for them.

Best regards,
--
Daniel Vérité
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