Re: Patch for psql History Display on MacOSX - Mailing list pgsql-hackers

Hello again, just my thoughts…

in psql  \s without a file is nice for me iff going through less (e.g. pager), but for the most part it doesn't work at
allon mac-osx. so nothing to lose for the mac psql users. 

regards,
stepan

Am 03.09.2014 um 07:45 schrieb Noah Misch <noah@leadboat.com>:

> On Tue, Sep 02, 2014 at 09:49:56AM -0400, Tom Lane wrote:
>> Noah Misch <noah@leadboat.com> writes:
>>> I'm with you that far.  Given a patch that does not change "\s /tmp/foo" and
>>> that makes "\s" equivalent to "\s /tmp/foo" + "\! cat /tmp/foo >/dev/tty",
>>> back-patch by all means.  No patch posted on this thread is so surgical, hence
>>> my objection.  In particular, your latest patch revision changes "\s /tmp/foo"
>>> to match the novel output the patch introduces for plain "\s".  "\s /tmp/foo"
>>> would no longer write data that libedit can reload as a history file.
>>
>> BTW, I failed last night to produce a coherent argument against that
>> particular point, but consider this.  What are the main use-cases for
>> \s to a file?  I argue that they are
>>
>>     1. Create a human-readable record of what you did.
>>     2. Create the starting point for a SQL script file.
>>
>> I do not deny it's possible that somebody out there is also using \s for
>>
>>     3. Create a file that I can overwrite ~/.psql_history with later.
>>
>> But if this is being done in the field at all, surely it is miles behind
>> the applications listed above.
>
> I'm unprepared to speculate about the relative prevalence of those use cases.
>
>> Now, if you are using libreadline, the output of \s has always been
>> perfectly fit for purposes 1 and 2, because it's plain text of the
>> history entries.  Moreover, it is *not* particularly fit for purpose 3,
>> because intra-command newlines aren't encoded.  Yes, you could get
>> libreadline to read the file, but multiline SQL commands will be seen
>> as multiple history entries which is very far from convenient to use.
>> (This adds to my suspicion that nobody is doing #3 in practice.)
>>
>> On the other hand, if you are using libedit, purpose 3 works great
>> but the output is utterly unfit for either purpose 1 or 2.  Here
>> are the first few lines of ~/.psql_history on one of my Macs:
>>
>> _HiStOrY_V2_
>> explain\040verbose\^A\040\040select\0401\^Aunion\^A\040\040select\0402;
>> \\q
>> select\0404;
>> explain\040verbose\^A\040\040select\0401\^Aunion\^A\040\040select\0402;
>> select\04044;
>> \\q
>> \\s
>> \\s\040foobar
>> \\q
>>
>> What the proposed patch does is ensure that \s produces plain text
>> regardless of which history library you are using.  I think arguing
>> that we shouldn't do that is stretching the concept of backwards
>> compatibility well past the breaking point.
>
> Given the negligible urgency to improve \s, the slightest compatibility hazard
> justifies punting this work from back-patch to master-only.
>
>
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