Message-ID: <491DC5F3D279CD4EB4B157DDD62237F406ABE859@zipwire.esri.com>
From: Jerry Day <jerry_day@esri.com>
To: "'Bruce Momjian'" <pgman@candle.pha.pa.us>, Jerry Day <jerry_day@esri.com>
Cc: "'pgsql-interfaces@postgresql.org'" <pgsql-interfaces@postgresql.org>
Subject: Re: Problems with PQfmod() returning -1 on varchar f
Date: Mon, 4 Apr 2005 10:54:15 -0700 
MIME-Version: 1.0
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	charset="iso-8859-1"

Bruce,

Thanks for your quick response. The column in question is defined as 'DATA
VARCHAR(20) NOT NULL'. The issue occurs when this is referenced in a fairly
complex query, such as:

SELECT data,int16_col,int64_col,float32_col,float64_col,
       date_col,row_id
FROM 
(SELECT b.data,b.int16_col,b.int64_col,
  b.float3_col,b.float64_col,b.date_col,b.row_id 
 FROM  table1 b  
 LEFT JOIN 
 (SELECT * 
  FROM table3 
 ) d ON b.ROW_ID = d.ROW_ID 
 WHERE d.ROW_ID IS NULL 
 UNION ALL 
 SELECT a.data,a.int16_col,a.int64_col,a.float32_col,
       a.float6_col,a.date_col,a.row_id
 FROM  table2 a  
 LEFT JOIN 
 (SELECT * 
  FROM table3 
 ) d ON (a.ROW_ID = d.ROW_ID) 
 WHERE d.ROW_ID IS NULL 
) V__282 LIMIT 0;

Where:

CREATE TABLE table1
(
  data varchar(20) NOT NULL,
  int16_col int2,
  int64_col int8,
  float32_col float4,
  float64_col float8,
  date_col timestamp,
  row_id int4 NOT NULL,
  CONSTRAINT table1_pk PRIMARY KEY (row_id)
) 
WITHOUT OIDS;

CREATE TABLE table2
(
  data varchar(20) NOT NULL,
  int16_col int2,
  int64_col int8,
  float32_col float4,
  float64_col float8,
  date_col timestamp,
  row_id int4 NOT NULL,
  CONSTRAINT table2_pk PRIMARY KEY (row_id)
) 
WITHOUT OIDS;

CREATE TABLE table3
(
  row_id int8 NOT NULL,
  int32_col int4 NOT NULL,
  int64_col int8 NOT NULL,
  CONSTRAINT table3_pk PRIMARY KEY (row_id)
) 
WITHOUT OIDS;

In this particular case, I can go back and describe each of the referenced
tables, but there are other times in our application where this is not
practical. Can you recommend a more reliable method to describe such
queries? Is this a current limitation in Postgres which may be addressed at
a future release?

Thanks,

Jerry

_|_|
_|_| ESRI
Jerry L. Day
Software Developer
(909)793-2853 Ext. 1477
jerry_day@esri.com

-----Original Message-----
From: Bruce Momjian [mailto:pgman@candle.pha.pa.us]
Sent: Saturday, April 02, 2005 5:27 PM
To: Jerry Day
Cc: 'pgsql-interfaces@postgresql.org'
Subject: Re: [INTERFACES] Problems with PQfmod() returning -1 on varchar
field (libpq-8.0.0 )?


Jerry Day wrote:
> Hi all,
> 
> I've recently encountered a situation where PQfmod() fails to return the
> defined length of a varchar field referenced in a query, as expected -
> returning no information (-1), instead. Has anyone else encountered this
> issue? If so, why does this occur? Can you recommended a method to more
> reliably obtain the length of varchar fields, as defined in the relations
> referenced by a query? 

Can we see the query?  I suspect the column is being manipulated in some
way and the length isn't carried through to the query output --- if so,
there might not be much we can do about it.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073