Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[David Steele]

On 12/23/15 9:15 PM, Michael Paquier wrote:

On Mon, Dec 7, 2015 at 9:14 PM, Michael Paquier
 wrote:

On Wed, Sep 2, 2015 at 6:19 AM, Marko Tiikkaja  wrote:

Hopefully nobody minds if I slip this to the commit fest that started
today?  The attached patch should address all the comments from the 9.5
cycle.

All the previous comments have been addressed. Perhaps some regression tests
would have some value?

This thread has been stalling for a couple of weeks now. I have marked
it as "returned with feedback". Marko, if you are still working on
this patch, could you add some regression tests and then move it to
the next CF?
This was submitted to the 2016-03 CF but no new patch was supplied and 
there's been no activity on the thread for months.  I'm marking it as 
"returned with feedback."


Marko, if can address Michael's concerns or supply a new patch I'll be 
happy to open the CF entry again.


Thanks,

--
-David
da...@pgmasters.net



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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Michael Paquier]

On Mon, Dec 7, 2015 at 9:14 PM, Michael Paquier
 wrote:
>
>
> On Wed, Sep 2, 2015 at 6:19 AM, Marko Tiikkaja  wrote:
>>
>> Hopefully nobody minds if I slip this to the commit fest that started
>> today?  The attached patch should address all the comments from the 9.5
>> cycle.
>
>
> All the previous comments have been addressed. Perhaps some regression tests
> would have some value?

This thread has been stalling for a couple of weeks now. I have marked
it as "returned with feedback". Marko, if you are still working on
this patch, could you add some regression tests and then move it to
the next CF?
-- 
Michael


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Michael Paquier]

On Wed, Sep 2, 2015 at 6:19 AM, Marko Tiikkaja  wrote:

> Hopefully nobody minds if I slip this to the commit fest that started
> today?  The attached patch should address all the comments from the 9.5
> cycle.
>

All the previous comments have been addressed. Perhaps some regression
tests would have some value?
-- 
Michael

Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

On 2015-09-01 23:19, I wrote:

Hopefully nobody minds if I slip this to the commit fest that started
today?  The attached patch should address all the comments from the 9.5
cycle.


Apparently the CF app will.  Meh.  Whatever.  Ignore then, I guess.


.m


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

Hi,

Hopefully nobody minds if I slip this to the commit fest that started 
today?  The attached patch should address all the comments from the 9.5 
cycle.



.m
*** a/src/backend/parser/analyze.c
--- b/src/backend/parser/analyze.c
***
*** 2107,2118  transformUpdateTargetList(ParseState *pstate, List 
*origTlist)
attrno = attnameAttNum(pstate->p_target_relation,
   origTarget->name, 
true);
if (attrno == InvalidAttrNumber)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg("column \"%s\" of relation 
\"%s\" does not exist",
origTarget->name,
!
RelationGetRelationName(pstate->p_target_relation)),
 parser_errposition(pstate, 
origTarget->location)));
  
updateTargetListEntry(pstate, tle, origTarget->name,
  attrno,
--- 2107,2136 
attrno = attnameAttNum(pstate->p_target_relation,
   origTarget->name, 
true);
if (attrno == InvalidAttrNumber)
+   {
+   bool need_hint = false;
+ 
+   /*
+* Table-qualifying the LHS expression in SET is a 
common mistake;
+* provide a hint if that seems to be the problem.
+*/
+   if (origTarget->indirection != NIL &&
+   IsA(linitial(origTarget->indirection), String))
+   {
+   if (strcmp(origTarget->name, 
RelationGetRelationName(pstate->p_target_relation)) == 0)
+   need_hint = true;
+   else if (target_rte->alias && 
strcmp(origTarget->name, target_rte->alias->aliasname) == 0)
+   need_hint = true;
+   }
+ 
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg("column \"%s\" of relation 
\"%s\" does not exist",
origTarget->name,
!   
RelationGetRelationName(pstate->p_target_relation)),
!need_hint ? errhint("Do not qualify an 
UPDATE target column with the name of the table.") : 0,
 parser_errposition(pstate, 
origTarget->location)));
+   }
  
updateTargetListEntry(pstate, tle, origTarget->name,
  attrno,

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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Michael Paquier]

On Thu, Jan 8, 2015 at 2:28 AM, Marko Tiikkaja ma...@joh.to wrote:
 Yeah.  (The CF entry is also set to Waiting on Author, which seems
 appropriate.)
Seeing nothing happening here for quite some time, marked as returned
with feedback..
-- 
Michael


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Alvaro Herrera]

We're waiting for an updated version here, right?

-- 
Álvaro Herrerahttp://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training  Services


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

On 1/7/15 6:22 PM, Alvaro Herrera wrote:

We're waiting for an updated version here, right?


Yeah.  (The CF entry is also set to Waiting on Author, which seems 
appropriate.)



.marko


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

On 2014-11-22 05:11, Peter Geoghegan wrote:

On Fri, Nov 21, 2014 at 7:49 PM, Marko Tiikkaja ma...@joh.to wrote:

A common mistake is to try and qualify column references on the LHS of SET
in UPDATE.


I think that this is a good idea, but as written the patch doesn't
handle aliases correctly:

postgres=# create table foo (val text);
CREATE TABLE
postgres=# update foo f set val = 'bar' where f.val != 'fd';
UPDATE 0
postgres=# update foo f set f.val = 'bar' where f.val != 'fd';
ERROR:  42703: column f of relation foo does not exist
LINE 1: update foo f set f.val = 'bar' where f.val != 'fd';
  ^
LOCATION:  transformUpdateStmt, analyze.c:2015


Good point!  Changed in v2, attached.


.marko
*** a/src/backend/parser/analyze.c
--- b/src/backend/parser/analyze.c
***
*** 1989,2000  transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
attrno = attnameAttNum(pstate-p_target_relation,
   origTarget-name, 
true);
if (attrno == InvalidAttrNumber)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg(column \%s\ of relation 
\%s\ does not exist,
origTarget-name,
!
RelationGetRelationName(pstate-p_target_relation)),
 parser_errposition(pstate, 
origTarget-location)));
  
updateTargetListEntry(pstate, tle, origTarget-name,
  attrno,
--- 1989,2020 
attrno = attnameAttNum(pstate-p_target_relation,
   origTarget-name, 
true);
if (attrno == InvalidAttrNumber)
+   {
+   const char *targetrefname;
+   const char *message_hint = NULL;
+ 
+   /*
+* Table-qualifying the LHS expression in SET is a 
common mistake;
+* provide a hint if that seems to be the problem.
+*/
+   if (target_rte-alias)
+   targetrefname = target_rte-alias-aliasname;
+   else
+   targetrefname = 
RelationGetRelationName(pstate-p_target_relation);
+ 
+   if (strcmp(origTarget-name, targetrefname) == 0 
+   origTarget-indirection != NIL 
+   IsA(linitial(origTarget-indirection), String))
+   message_hint = Target column references in 
UPDATE must not be qualified;
+ 
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg(column \%s\ of relation 
\%s\ does not exist,
origTarget-name,
!   
RelationGetRelationName(pstate-p_target_relation)),
!message_hint ? errhint(%s, 
message_hint) : 0,
 parser_errposition(pstate, 
origTarget-location)));
+   }
  
updateTargetListEntry(pstate, tle, origTarget-name,
  attrno,

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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Tom Lane]

Marko Tiikkaja ma...@joh.to writes:
 A common mistake is to try and qualify column references on the LHS of 
 SET in UPDATE.  The error message can be a bit cryptic at times, too. 

Perhaps, but this hint is not much of an improvement:

 HINT:  Target column references in UPDATE must not be qualified

because target column references *can* be qualified, for example
if you have a composite column datatype you can assign directly to
one of its fields.  (This ambiguity is exactly why we don't simply
allow the case.)  So I don't think that qualified is a sufficiently
precise phrase to be helpful.  Possibly something along the lines of

HINT:  Do not qualify an UPDATE target column with the name of the table.

Also, the coding technique used here is poor, because the hint text
will not be exposed for translation.  The usual pattern is

 need_hint ? errhint(Message text here.) : 0

Also, as far as Peter's point goes, it would likely make sense to
issue this hint if the column basename is *either* the alias name
or the underlying table name.

regards, tom lane


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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

On 2014-11-22 18:02, Tom Lane wrote:

Marko Tiikkaja ma...@joh.to writes:

A common mistake is to try and qualify column references on the LHS of
SET in UPDATE.  The error message can be a bit cryptic at times, too.


Perhaps, but this hint is not much of an improvement:


HINT:  Target column references in UPDATE must not be qualified


because target column references *can* be qualified, for example
if you have a composite column datatype you can assign directly to
one of its fields.  (This ambiguity is exactly why we don't simply
allow the case.)  So I don't think that qualified is a sufficiently
precise phrase to be helpful.  Possibly something along the lines of

HINT:  Do not qualify an UPDATE target column with the name of the table.


Sounds good to me.  I didn't expect anyone to like the wording of the 
hint in the first place ;-)



Also, the coding technique used here is poor, because the hint text
will not be exposed for translation.  The usual pattern is

  need_hint ? errhint(Message text here.) : 0


Oops.  I just copied what the first relevant grep of errhint did, which 
was from postgres_fdw.  But its hints will already have been translated. 
 Will fix.



Also, as far as Peter's point goes, it would likely make sense to
issue this hint if the column basename is *either* the alias name
or the underlying table name.


Yeah, I thought about that too, but I thought that might be weird if 
there's an alias in FROM with the name of the table, e.g:


  UPDATE foo f1 SET foo.a = 1 FROM foo;

But I don't really care too much either way.


.marko


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[HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Marko Tiikkaja]

Hi,

A common mistake is to try and qualify column references on the LHS of 
SET in UPDATE.  The error message can be a bit cryptic at times, too. 
I've attached a patch to try and improve the situation a bit:


=# create table foo(bar int);
CREATE TABLE

=# update foo set foo.bar = 1;
ERROR:  column foo of relation foo does not exist
LINE 1: update foo set foo.bar = 1;
   ^
HINT:  Target column references in UPDATE must not be qualified

=# update foo set notfoo.bar = 1; -- no hint
ERROR:  column notfoo of relation foo does not exist
LINE 1: update foo set notfoo.bar = 1;
   ^

=# update foo set foo.bar[1] = 1;
ERROR:  column foo of relation foo does not exist
LINE 1: update foo set foo.bar[1] = 1;
   ^
HINT:  Target column references in UPDATE must not be qualified


I'll add this to the next CF, but feel free to bash it before that.


.marko
*** a/src/backend/parser/analyze.c
--- b/src/backend/parser/analyze.c
***
*** 1989,2000  transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
attrno = attnameAttNum(pstate-p_target_relation,
   origTarget-name, 
true);
if (attrno == InvalidAttrNumber)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg(column \%s\ of relation 
\%s\ does not exist,
origTarget-name,
!
RelationGetRelationName(pstate-p_target_relation)),
 parser_errposition(pstate, 
origTarget-location)));
  
updateTargetListEntry(pstate, tle, origTarget-name,
  attrno,
--- 1989,2019 
attrno = attnameAttNum(pstate-p_target_relation,
   origTarget-name, 
true);
if (attrno == InvalidAttrNumber)
+   {
+   const char *relname;
+   const char *message_hint = NULL;
+ 
+   /*
+* Table-qualifying the LHS expression in SET is a 
common mistake;
+* provide a hint if that seems to be the problem.
+*/
+   relname = 
RelationGetRelationName(pstate-p_target_relation);
+   if (strcmp(origTarget-name, relname) == 0 
+   origTarget-indirection != NIL)
+   {
+   Node *ind = linitial(origTarget-indirection);
+   if (IsA(ind, String))
+   message_hint = Target column 
references in UPDATE must not be qualified;
+   }
+ 
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_COLUMN),
 errmsg(column \%s\ of relation 
\%s\ does not exist,
origTarget-name,
!   relname),
!message_hint ? errhint(%s, 
message_hint) : 0,
 parser_errposition(pstate, 
origTarget-location)));
+   }
  
updateTargetListEntry(pstate, tle, origTarget-name,
  attrno,

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Re: [HACKERS] HINTing on UPDATE foo SET foo.bar = ..;

[Peter Geoghegan]

On Fri, Nov 21, 2014 at 7:49 PM, Marko Tiikkaja ma...@joh.to wrote:
 A common mistake is to try and qualify column references on the LHS of SET
 in UPDATE.

I think that this is a good idea, but as written the patch doesn't
handle aliases correctly:

postgres=# create table foo (val text);
CREATE TABLE
postgres=# update foo f set val = 'bar' where f.val != 'fd';
UPDATE 0
postgres=# update foo f set f.val = 'bar' where f.val != 'fd';
ERROR:  42703: column f of relation foo does not exist
LINE 1: update foo f set f.val = 'bar' where f.val != 'fd';
 ^
LOCATION:  transformUpdateStmt, analyze.c:2015

-- 
Peter Geoghegan


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