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Thread: psql UPDATE field [tab] expands to DEFAULT?

psql UPDATE field [tab] expands to DEFAULT?

From
Ken Tanzer
Date:
Hi.  If I'm using psql, and type for example:

UPDATE my_table SET my_field 
(with a trailing space)

and then hit Tab, it will expand that to an =, and then another tab will expand to DEFAULT, so that I then have:

UPDATE my_table SET my_field = DEFAULT

If I'm tabbing out in this situation, it's going to be after the =, and I will have typed "myreal"[tab] in the vain hope that psql will complete that to "myreallylongfieldname," but instead it gets replaced with DEFAULT.

So I'm curious if this is intended behavior, if it's considered useful, and/or if it's a placeholder for something in the future that will be useful.  Also, is this new, as I've never noticed it before?

Thanks in advance,
Ken

p.s.,  Version 9.6.13

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Re: psql UPDATE field [tab] expands to DEFAULT?

From
Adrian Klaver
Date:
On 6/17/19 3:03 PM, Ken Tanzer wrote:
> Hi.  If I'm using psql, and type for example:
> 
> UPDATE my_table SET my_field
> (with a trailing space)
> 
> and then hit Tab, it will expand that to an =, and then another tab will 
> expand to DEFAULT, so that I then have:
> 
> UPDATE my_table SET my_field = DEFAULT
> 
> If I'm tabbing out in this situation, it's going to be after the =, and 
> I will have typed "myreal"[tab] in the vain hope that psql will complete 
> that to "myreallylongfieldname," but instead it gets replaced with DEFAULT.
> 
> So I'm curious if this is intended behavior, if it's considered useful, 
> and/or if it's a placeholder for something in the future that will be 
> useful.  Also, is this new, as I've never noticed it before?

Not sure how long that has been around.

My cheat for dealing with many/long column names is:

test=# \d up_test
               Table "public.up_test"
  Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------
  id     | integer |           |          |
  col1   | boolean |           |          |
  col2   | integer |           |          |



test=# \pset format unaligned
Output format is unaligned.
test=# \pset fieldsep ','
Field separator is ",".

select * from up_test limit 0;
id,col1,col2

Cut and paste above.

test=# \pset fieldsep '|'
Field separator is "|".

test=# \pset format 'aligned'
Output format is aligned.


> 
> Thanks in advance,
> Ken
> 
> p.s.,  Version 9.6.13
> 
> -- 
> AGENCY Software
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> By and for non-profits
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> ken.tanzer@agency-software.org <mailto:ken.tanzer@agency-software.org>
> (253) 245-3801
> 
> Subscribe to the mailing list 
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> follow the discussion.


-- 
Adrian Klaver
adrian.klaver@aklaver.com

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Ken Tanzer
Date:
On Mon, Jun 17, 2019 at 4:24 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 6/17/19 3:03 PM, Ken Tanzer wrote:
>
> So I'm curious if this is intended behavior, if it's considered useful,
> and/or if it's a placeholder for something in the future that will be
> useful.  Also, is this new, as I've never noticed it before?

Not sure how long that has been around.

My cheat for dealing with many/long column names is:


Thanks Adrian, though I wasn't really seeking tips for column names.  I was instead trying to understand whether this particular tab expansion was intentional and considered useful, and if so what that usefulness was, because it's rather escaping me!

Cheers,
Ken


-- 
AGENCY Software  
A Free Software data system
By and for non-profits
(253) 245-3801

learn more about AGENCY or
follow the discussion.

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Tim Cross
Date:


On Tue, 18 Jun 2019 at 09:34, Ken Tanzer <ken.tanzer@gmail.com> wrote:
On Mon, Jun 17, 2019 at 4:24 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 6/17/19 3:03 PM, Ken Tanzer wrote:
>
> So I'm curious if this is intended behavior, if it's considered useful,
> and/or if it's a placeholder for something in the future that will be
> useful.  Also, is this new, as I've never noticed it before?

Not sure how long that has been around.

My cheat for dealing with many/long column names is:


Thanks Adrian, though I wasn't really seeking tips for column names.  I was instead trying to understand whether this particular tab expansion was intentional and considered useful, and if so what that usefulness was, because it's rather escaping me!

Cheers,
Ken



Have to say, I fid that behaviour unusual as well. I would expect that once I've typed some characters, the completion mechanism would attempt to complete based on the characters I've typed and if it cannot, to do nothing. Instead, what happens is that what I have typed is replaced by 'default'.  For example, if I type

update my_table set my_col = other_t

and hit tab, 'other_t is replaced by 'default', which is of no use. What I would expect is for tab to either complete (possibly only partially if there is multiple candidates) what it could for candidates which start with 'other_t' e.g. 'other_table' or it would do nothing i.e. no completion candidates found, telling me there is no match based on the prefix I've typed.

 
--
regards,

Tim

--
Tim Cross

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Adrian Klaver
Date:
On 6/17/19 4:33 PM, Ken Tanzer wrote:
> On Mon, Jun 17, 2019 at 4:24 PM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> wrote:
> 
>     On 6/17/19 3:03 PM, Ken Tanzer wrote:
>      >
>      > So I'm curious if this is intended behavior, if it's considered
>     useful,
>      > and/or if it's a placeholder for something in the future that
>     will be
>      > useful.  Also, is this new, as I've never noticed it before?
> 
>     Not sure how long that has been around.
> 
>     My cheat for dealing with many/long column names is:
> 
> 
> Thanks Adrian, though I wasn't really seeking tips for column names.  I 
> was instead trying to understand whether this particular tab expansion 
> was intentional and considered useful, and if so what that usefulness 

If I am following the below correctly it is intentional:


https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/bin/psql/tab-complete.c;h=68a2ba27aec22302625c5481a8f74cf866f4dc23;hb=d22ca701a39dfd03cdfa1ca238370d34f4bc4ac4

Line 2888

Useful, that is in the eye of the beholder:)

> was, because it's rather escaping me!
> 
> Cheers,
> Ken
> 
> 



-- 
Adrian Klaver
adrian.klaver@aklaver.com

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Jeff Janes
Date:
On Mon, Jun 17, 2019 at 6:03 PM Ken Tanzer <ken.tanzer@gmail.com> wrote:
Hi.  If I'm using psql, and type for example:

UPDATE my_table SET my_field 
(with a trailing space)

and then hit Tab, it will expand that to an =, and then another tab will expand to DEFAULT, so that I then have:

UPDATE my_table SET my_field = DEFAULT

If I'm tabbing out in this situation, it's going to be after the =, and I will have typed "myreal"[tab] in the vain hope that psql will complete that to "myreallylongfieldname," but instead it gets replaced with DEFAULT.

Yeah, it is especially annoying to delete what I actually typed to replace it with something else.  I've been irked by that before.  I think the general behavior of replacing something already typed with (what it believes to be) the only proper completion is part of the underlying readline/libedit library, not something psql goes out of its way to do.
 
So I'm curious if this is intended behavior, if it's considered useful, and/or if it's a placeholder for something in the future that will be useful.  Also, is this new, as I've never noticed it before?

The tab completion doesn't have a SQL parser/analyzer, it is just driven of general rules of looking at the proceeding N words.  In this case, it is hitting the rule for "SET anything TO", which is intended to catch the setting of parameters, it is only accidentally hitting on the SET part of UPDATE statements.

This goes back at least to 9.3.

We could improve it by making a higher priority rule which looks back a few more words to:

UPDATE <tablename> SET <colname> TO

But what would we complete with?  Any expression can go there, and we can't make it tab complete any arbitrary expression, like function names or literals.  If we tab complete, but only with a restricted set of choices, that could be interpreted as misleadingly suggesting no other things are possible.  (Of course the current accidental behavior is also misleading, then) 

If we are willing to offer an incomplete list of suggestions, what would they be?  NULL, DEFAULT, '(' and all the columnnames present in <tablename>, with appropriate quotes where necessary?  But what to do with <tablename> doesn't actually exist as the name of a table?

Or, we could have it implement the more precise higher priority rule, and have it just refuse to offer any suggestions, but at least not delete what is already there.

Cheers,

Jeff

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Jeff Janes
Date:
On Mon, Jun 17, 2019 at 8:23 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 6/17/19 4:33 PM, Ken Tanzer wrote:
>
> Thanks Adrian, though I wasn't really seeking tips for column names.  I
> was instead trying to understand whether this particular tab expansion
> was intentional and considered useful, and if so what that usefulness

If I am following the below correctly it is intentional:

https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/bin/psql/tab-complete.c;h=68a2ba27aec22302625c5481a8f74cf866f4dc23;hb=d22ca701a39dfd03cdfa1ca238370d34f4bc4ac4

Line 2888

But that portion doesn't offer the DEFAULT completion.  It stops at offering '=', and goes no further.

It is at line 2859 which accidentally offers to complete DEFAULT, and that is not part of the UPDATE-specific code.
 
Cheers,

Jeff

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Tom Lane
Date:
Tim Cross <theophilusx@gmail.com> writes:
> On Tue, 18 Jun 2019 at 09:34, Ken Tanzer <ken.tanzer@gmail.com> wrote:
>> Thanks Adrian, though I wasn't really seeking tips for column names.  I
>> was instead trying to understand whether this particular tab expansion was
>> intentional and considered useful, and if so what that usefulness was,
>> because it's rather escaping me!

> Have to say, I fid that behaviour unusual as well.

I don't think it's intentional.  A look into tab-complete.c shows that it
makes no attempt to offer completions beyond the "=" part of the syntax;
so there's room for improvement there.  But then what is producing the
"DEFAULT" completion?  After looking around a bit, I think it's
accidentally matching the pattern for a GUC "set" command:

    else if (TailMatches("SET", MatchAny, "TO|="))
    {
        /* special cased code for individual GUCs */
        ...
        else
            COMPLETE_WITH("DEFAULT");
    }

So perhaps that needs to look more like this other place where somebody
already noticed the conflict against UPDATE:

    else if (TailMatches("SET|RESET") && !TailMatches("UPDATE", MatchAny, "SET"))
        COMPLETE_WITH_QUERY(Query_for_list_of_set_vars);

More generally, though, I'm inclined to think that offering DEFAULT
and nothing else, which is what this code does if it doesn't recognize
the "GUC name", is just ridiculous.  If the word after SET is not a known
GUC name then we probably have misconstrued the context, as indeed is
happening in your example; and in any case DEFAULT is about the least
likely thing for somebody to be trying to enter here.  (They'd probably
have selected RESET not SET if they were trying to do that.)

            regards, tom lane

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Tim Cross
Date:


On Tue, 18 Jun 2019 at 10:39, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Tim Cross <theophilusx@gmail.com> writes:
> On Tue, 18 Jun 2019 at 09:34, Ken Tanzer <ken.tanzer@gmail.com> wrote:
>> Thanks Adrian, though I wasn't really seeking tips for column names.  I
>> was instead trying to understand whether this particular tab expansion was
>> intentional and considered useful, and if so what that usefulness was,
>> because it's rather escaping me!

> Have to say, I fid that behaviour unusual as well.

I don't think it's intentional.  A look into tab-complete.c shows that it
makes no attempt to offer completions beyond the "=" part of the syntax;
so there's room for improvement there.  But then what is producing the
"DEFAULT" completion?  After looking around a bit, I think it's
accidentally matching the pattern for a GUC "set" command:

    else if (TailMatches("SET", MatchAny, "TO|="))
    {
        /* special cased code for individual GUCs */
        ...
        else
            COMPLETE_WITH("DEFAULT");
    }

So perhaps that needs to look more like this other place where somebody
already noticed the conflict against UPDATE:

    else if (TailMatches("SET|RESET") && !TailMatches("UPDATE", MatchAny, "SET"))
        COMPLETE_WITH_QUERY(Query_for_list_of_set_vars);

More generally, though, I'm inclined to think that offering DEFAULT
and nothing else, which is what this code does if it doesn't recognize
the "GUC name", is just ridiculous.  If the word after SET is not a known
GUC name then we probably have misconstrued the context, as indeed is
happening in your example; and in any case DEFAULT is about the least
likely thing for somebody to be trying to enter here.  (They'd probably
have selected RESET not SET if they were trying to do that.)

                        regards, tom lane


Given that without adding a full blown sql parser in order to identify legitimate candidates following a '=' in an update statement, my suggestion would be to refine the rules so that no completion is attempted after the =. Would rather have tab do nothing over tab replacing what I've already typed with 'default'. 

--
regards,

Tim

--
Tim Cross

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Ken Tanzer
Date:
On Mon, Jun 17, 2019 at 4:24 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:

My cheat for dealing with many/long column names is:

test=# \d up_test
               Table "public.up_test"
  Column |  Type   | Collation | Nullable | Default
--------+---------+-----------+----------+---------
  id     | integer |           |          |
  col1   | boolean |           |          |
  col2   | integer |           |          |



test=# \pset format unaligned
Output format is unaligned.
test=# \pset fieldsep ','
Field separator is ",".

select * from up_test limit 0;
id,col1,col2

Cut and paste above.

test=# \pset fieldsep '|'
Field separator is "|".

test=# \pset format 'aligned'
Output format is aligned.


Just curious, but if you really do that often, wouldn't you be better off with something like this?

CREATE OR REPLACE FUNCTION field_list( name ) RETURNS text AS $$

SELECT array_to_string(array_agg(column_name::text ORDER BY ordinal_position),',') FROM information_schema.columns WHERE table_name = $1;

$$ LANGUAGE sql STABLE;

Cheers,
Ken



--
AGENCY Software  
A Free Software data system
By and for non-profits
(253) 245-3801

learn more about AGENCY or
follow the discussion.

Re: psql UPDATE field [tab] expands to DEFAULT?

From
Adrian Klaver
Date:
On 6/18/19 3:23 PM, Ken Tanzer wrote:
> On Mon, Jun 17, 2019 at 4:24 PM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> wrote:
> 
> 
>     My cheat for dealing with many/long column names is:
> 
>     test=# \d up_test
>                     Table "public.up_test"
>        Column |  Type   | Collation | Nullable | Default
>     --------+---------+-----------+----------+---------
>        id     | integer |           |          |
>        col1   | boolean |           |          |
>        col2   | integer |           |          |
> 
> 
> 
>     test=# \pset format unaligned
>     Output format is unaligned.
>     test=# \pset fieldsep ','
>     Field separator is ",".
> 
>     select * from up_test limit 0;
>     id,col1,col2
> 
>     Cut and paste above.
> 
>     test=# \pset fieldsep '|'
>     Field separator is "|".
> 
>     test=# \pset format 'aligned'
>     Output format is aligned.
> 
> 
> Just curious, but if you really do that often, wouldn't you be better 
> off with something like this?

I could/should I just don't do the above enough to get motivated to 
build a function. Most cases where I'm doing complicated updates I am 
not using psql I am building then in Python from a dict.

> 
> CREATE OR REPLACE FUNCTION field_list( name ) RETURNS text AS $$
> 
> SELECT array_to_string(array_agg(column_name::text ORDER BY 
> ordinal_position),',') FROM information_schema.columns WHERE table_name 
> = $1;
> 
> $$ LANGUAGE sql STABLE;
> 
> Cheers,
> Ken
> 



-- 
Adrian Klaver
adrian.klaver@aklaver.com