Which view has cache_value of sequences? - postgresql

Question

I'm building a query which retrieves a list of sequences on pgsql-9.1.6. Please see my SQL set below...
mydb=# create sequence seq1 cache 10;
CREATE SEQUENCE
mydb=# create sequence seq2 cache 20;
CREATE SEQUENCE
mydb=# \ds
List of relations
Schema | Name | Type | Owner
--------+------+----------+-------
public | seq1 | sequence | pgdba
public | seq2 | sequence | pgdba
(2 rows)
mydb=# \x
Expanded display is on.
mydb=# select * from seq1;
-[ RECORD 1 ]-+--------------------
sequence_name | seq1
last_value | 1
start_value | 1
increment_by | 1
max_value | 9223372036854775807
min_value | 1
cache_value | 10
log_cnt | 0
is_cycled | f
is_called | f
mydb=# select * from seq2;
-[ RECORD 1 ]-+--------------------
sequence_name | seq2
last_value | 1
start_value | 1
increment_by | 1
max_value | 9223372036854775807
min_value | 1
cache_value | 20
log_cnt | 0
is_cycled | f
is_called | f
mydb=# select * from information_schema.sequences;
-[ RECORD 1 ]-----------+--------------------
sequence_catalog | mydb
sequence_schema | public
sequence_name | seq1
data_type | bigint
numeric_precision | 64
numeric_precision_radix | 2
numeric_scale | 0
start_value | 1
minimum_value | 1
maximum_value | 9223372036854775807
increment | 1
cycle_option | NO
-[ RECORD 2 ]-----------+--------------------
sequence_catalog | mydb
sequence_schema | public
sequence_name | seq2
data_type | bigint
numeric_precision | 64
numeric_precision_radix | 2
numeric_scale | 0
start_value | 1
minimum_value | 1
maximum_value | 9223372036854775807
increment | 1
cycle_option | NO
information_schema.sequences has no cache_value. Which view can I join to get cache_value with my sequence list?

Answer 1

Best I'm aware, you're actually viewing where this data is stored right there... The table name is that of the sequence itself. There is no view in the formation schema because it's an implementation detail relatd to Postgres.
Side note: Postgres uses the pg_catalog to create views for within the information schema. The latter really is a cross-platform convenience; the real details are in the catalog. Don't miss psql's --echo-hidden option to find out more about the internals:
http://www.postgresql.org/docs/current/static/app-psql.html
# Output using `psql -E`
test=# create sequence test;
CREATE SEQUENCE
test=# \d+ test
********* QUERY **********
SELECT c.oid,
n.nspname,
c.relname
FROM pg_catalog.pg_class c
LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
WHERE c.relname ~ '^(test)$'
AND pg_catalog.pg_table_is_visible(c.oid)
ORDER BY 2, 3;
**************************
********* QUERY **********
SELECT c.relchecks, c.relkind, c.relhasindex, c.relhasrules, c.relhastriggers, c.relhasoids, pg_catalog.array_to_string(c.reloptions || array(select 'toast.' || x from pg_catalog.unnest(tc.reloptions) x), ', ')
, c.reltablespace, CASE WHEN c.reloftype = 0 THEN '' ELSE c.reloftype::pg_catalog.regtype::pg_catalog.text END, c.relpersistence
FROM pg_catalog.pg_class c
LEFT JOIN pg_catalog.pg_class tc ON (c.reltoastrelid = tc.oid)
WHERE c.oid = '25356';
**************************
********* QUERY **********
SELECT * FROM public.test;
**************************
********* QUERY **********
SELECT a.attname,
pg_catalog.format_type(a.atttypid, a.atttypmod),
(SELECT substring(pg_catalog.pg_get_expr(d.adbin, d.adrelid) for 128)
FROM pg_catalog.pg_attrdef d
WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef),
a.attnotnull, a.attnum,
(SELECT c.collname FROM pg_catalog.pg_collation c, pg_catalog.pg_type t
WHERE c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <> t.typcollation) AS attcollation,
NULL AS indexdef,
NULL AS attfdwoptions,
a.attstorage,
CASE WHEN a.attstattarget=-1 THEN NULL ELSE a.attstattarget END AS attstattarget
FROM pg_catalog.pg_attribute a
WHERE a.attrelid = '25356' AND a.attnum > 0 AND NOT a.attisdropped
ORDER BY a.attnum;
**************************
********* QUERY **********
SELECT pg_catalog.quote_ident(nspname) || '.' ||
pg_catalog.quote_ident(relname) || '.' ||
pg_catalog.quote_ident(attname)
FROM pg_catalog.pg_class c
INNER JOIN pg_catalog.pg_depend d ON c.oid=d.refobjid
INNER JOIN pg_catalog.pg_namespace n ON n.oid=c.relnamespace
INNER JOIN pg_catalog.pg_attribute a ON (
a.attrelid=c.oid AND
a.attnum=d.refobjsubid)
WHERE d.classid='pg_catalog.pg_class'::pg_catalog.regclass
AND d.refclassid='pg_catalog.pg_class'::pg_catalog.regclass
AND d.objid=25356
AND d.deptype='a'
**************************
Sequence "public.test"
Column | Type | Value | Storage
---------------+---------+---------------------+---------
sequence_name | name | test | plain
last_value | bigint | 1 | plain
start_value | bigint | 1 | plain
increment_by | bigint | 1 | plain
max_value | bigint | 9223372036854775807 | plain
min_value | bigint | 1 | plain
cache_value | bigint | 1 | plain
log_cnt | bigint | 0 | plain
is_cycled | boolean | f | plain
is_called | boolean | f | plain
test=#