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Trying to understand pg_get_expr()
2+ messages / 2 participants
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* Trying to understand pg_get_expr()
@ 2026-03-17 19:31 Adrian Klaver <[email protected]>
  2026-03-17 20:08 ` Re: Trying to understand pg_get_expr() Marcos Pegoraro <[email protected]>
  0 siblings, 1 reply; 2+ messages in thread

From: Adrian Klaver @ 2026-03-17 19:31 UTC (permalink / raw)
  To: pgsql-general

Given:

select version();
                   version 

-----------------------------------------------
  PostgreSQL 17.9 (Ubuntu 17.9-1.pgdg24.04+1)

and:

CREATE TABLE default_test (
     id integer,
     fld_1 varchar DEFAULT 'test',
     fld_2 integer DEFAULT 0
);

Then:

SELECT
     adrelid::regclass,
     pg_typeof(pg_get_expr(adbin, adrelid)),
     pg_get_expr(adbin, adrelid)
FROM
     pg_attrdef
WHERE
     adrelid = 'default_test'::regclass;

  adrelid    | pg_typeof |        pg_get_expr
--------------+-----------+---------------------------
  default_test | text      | 'test'::character varying
  default_test | text      | 0

and:

SELECT
     adrelid::regclass,
     pg_typeof(pg_get_expr(adbin, adrelid)),
     pg_get_expr(adbin, adrelid)
FROM
     pg_attrdef
WHERE
     adrelid = 'default_test'::regclass
     AND pg_get_expr(adbin, adrelid) = '0';

adrelid    | pg_typeof | pg_get_expr
--------------+-----------+-------------
  default_test | text      | 0


SELECT
     adrelid::regclass,
     pg_typeof(pg_get_expr(adbin, adrelid)),
     pg_get_expr(adbin, adrelid)
FROM
     pg_attrdef
WHERE
     adrelid = 'default_test'::regclass
     AND pg_get_expr(adbin, adrelid) = 'test';

adrelid | pg_typeof | pg_get_expr
---------+-----------+-------------
(0 rows)

Why does the = 'test' not return anything?

-- 
Adrian Klaver
[email protected]







^ permalink  raw  reply  [nested|flat] 2+ messages in thread

* Re: Trying to understand pg_get_expr()
  2026-03-17 19:31 Trying to understand pg_get_expr() Adrian Klaver <[email protected]>
@ 2026-03-17 20:08 ` Marcos Pegoraro <[email protected]>
  0 siblings, 0 replies; 2+ messages in thread

From: Marcos Pegoraro @ 2026-03-17 20:08 UTC (permalink / raw)
  To: Adrian Klaver <[email protected]>; +Cc: pgsql-general

Em ter., 17 de mar. de 2026 às 16:31, Adrian Klaver <
[email protected]> escreveu:

> Why does the = 'test' not return anything?


for me pg_get_expr(adbin, adrelid) returns 'test'::character varying
so it differs from 'test'

regards
Marcos


^ permalink  raw  reply  [nested|flat] 2+ messages in thread

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