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Thread: Explain verbose query with CTE

Explain verbose query with CTE

From
Bartosz Dmytrak
Date:
Hi,
This e-mail is reposted form pgadmin support mailing list. This problem looks like related with postgres not pgAdmin.

I faced strange problem (strange for me):
I have written code:

WITH t as (
INSERT INTO "tblD1" (id, "Data1")
VALUES ('a', 123)
RETURNING *)

UPDATE "tblBase"
SET "SomeData" = 123
WHERE id = 'a';


this code operates on simple tables:
CREATE TABLE "tblBase"(
  id text NOT NULL,
  "SomeData" integer,
  CONSTRAINT "tblBase_pkey" PRIMARY KEY (id )
)
WITH (OIDS=FALSE);

and

CREATE TABLE "tblD1" (
  id text NOT NULL,
  "Data1" integer,
  ser serial NOT NULL,
  CONSTRAINT "tblD1_pkey" PRIMARY KEY (id ),
  CONSTRAINT "tblD1_id_fkey" FOREIGN KEY (id)
      REFERENCES "tblBase" (id) MATCH FULL
      ON UPDATE CASCADE ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
)
WITH (OIDS=FALSE);

in table "tblBase" two record exist:

id ; "SomeData"
'3';345
'a';1

i tried to use Explain query functionality and then I received a message:
Query result with 0 rows will be returned.
ERROR:  cache lookup failed for attribute 3 of relation 38264
********** Error **********
ERROR: cache lookup failed for attribute 3 of relation 38264
SQL state: XX000

interesting thing is that execution of this code works as expected, also EXPLAIN and EXPLAIN ANALYZE gives proper response:
eg. EXPLAIN:
'Update on "tblBase"  (cost=0.01..1.04 rows=1 width=38)'
'  CTE t'
'    ->  Insert on "tblD1"  (cost=0.00..0.01 rows=1 width=0)'
'          ->  Result  (cost=0.00..0.01 rows=1 width=0)'
'  ->  Seq Scan on "tblBase"  (cost=0.00..1.02 rows=1 width=38)'
'        Filter: (id = 'a'::text)'


SELECT relname FROM pg_class WHERE oid = 38264;
gives "tblBase"

pg log lines look like this:
2012-04-18 22:44:25 CEST|myDatabase|postgres|pgAdmin III - Query Tool|myHost(59562)|6828LOG:  statement: EXPLAIN (ANALYZE off, VERBOSE on, COSTS on, BUFFERS off )WITH t as (
INSERT INTO "tblDerived1" (id, "Data1")
VALUES ('a', 123)
RETURNING *)
UPDATE "tblBase"
SET "SomeData" = (SELECT ser FROM t)
WHERE id = (SELECT id FROM t)
2012-04-18 22:44:25 CEST|myDatabase|postgres|pgAdmin III - Query Tool|myHost(59562)|6828ERROR:  cache lookup failed for attribute 3 of relation 38264
2012-04-18 22:44:25 CEST|myDatabase|postgres|pgAdmin III - Query Tool|myHost(59562)|6828STATEMENT:  EXPLAIN (ANALYZE off, VERBOSE on, COSTS on, BUFFERS off )WITH t as (
INSERT INTO "tblDerived1" (id, "Data1")
VALUES ('a', 123)
RETURNING *)
UPDATE "tblBase"
SET "SomeData" = (SELECT ser FROM t)
WHERE id = (SELECT id FROM t)

I think maybe VERBOSE option is a problem, but not sure.

environment:
pgAdmin 1.14.2 (Mandriva Linux 64 bit)
PostgreSQL 9.1.3 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-46), 64-bit


Thanks in advance for any help. 

Regards,
Bartek

Re: Explain verbose query with CTE

From
Tom Lane
Date:
Bartosz Dmytrak <bdmytrak@gmail.com> writes:
> This e-mail is reposted form pgadmin support mailing list. This problem
> looks like related with postgres not pgAdmin.
> [ EXPLAIN VERBOSE yields a "cache lookup failed" error ]

Huh, yeah, that's a backend bug all right.  I thought at first you might
have a catalog-corruption problem, but I can reproduce the failure here
from your example.  Most likely EXPLAIN is getting confused about which
Var belongs to which table.  Will look into it.

            regards, tom lane

Re: Explain verbose query with CTE

From
Bartosz Dmytrak
Date:
2012/4/20 Tom Lane <tgl@sss.pgh.pa.us>
 Will look into it.


Thanks again for Your time :)

Regards,
Bartek

Re: Explain verbose query with CTE

From
Tom Lane
Date:
Bartosz Dmytrak <bdmytrak@gmail.com> writes:
> [ EXPLAIN VERBOSE fails for ]
> WITH t as (
> INSERT INTO "tblD1" (id, "Data1")
>  VALUES ('a', 123)
> RETURNING *)
> UPDATE "tblBase"
> SET "SomeData" = 123
> WHERE id = 'a';

I've applied a patch for this.  Thanks for the report!

            regards, tom lane

Re: Explain verbose query with CTE

From
Bartosz Dmytrak
Date:
2012/4/26 Tom Lane <tgl@sss.pgh.pa.us>
I've applied a patch for this.  Thanks for the report!

                       regards, tom lane


Thanks for Your time :)

Regards,
Bartek