Re: stored function data structures - difficulty

Hello

2011/11/22 J.V. <jvsrvcs(at)gmail(dot)com>:
>
> I cannot find a way to programatically:
>    1.  Given a table name, find all foreign key fields in the given table by
> field name (column name)
>    2.  Given a single foreign key field name, programatically look up the
> corresponding reference table name and the reference primary key field
>
> so have thought of simply hard coding this (for 100 tables).
>
> What Kind of data structure could I use that is available to me that would
> hold as the key the table name and from there be able to iterate through and
> get all foreign keys by field name and from there another inner loop that
> would give me another key/value pair of the table name (key) and the primary
> key (value) that corresponds to that foreign key?
>
> I want to hard code all of this information into a data structure and
> iterate through at some point in another function.
>
> Instead of discovering this programatically, I can manually look at each
> table / schema diagram and hard code it, but I really need one super
> structure that will hold as keys every table in the schema and be able to
> drill down that that tables foreign keys and from there further drill down
> to get the table name, primary key field in that table.
>
> I have seen a number of structures that might work, but cannot find an
> example on how to actually use for what I need to do.  If you do have an
> idea of a structure, it would be great and awesome if I could be pointed to
> an actual working example that I could test in a sandbox first to understand
> how it works.
>

psql has a nice featute, that can help with orientation in system catalog

if I need a query, that describe a some database object, I need to
know a adequate psql meta statement. You have to run psql with -E
param, and then psql shows a queries that was necessary for processing
a statement

[pavel(at)nemesis ~]$ psql -E postgres
psql (9.2devel)
Type "help" for help.

postgres=# \d a1
********* 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 ~ '^(a1)$'
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, '', 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 = '146989';
**************************

********* 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
FROM pg_catalog.pg_attribute a
WHERE a.attrelid = '146989' AND a.attnum > 0 AND NOT a.attisdropped
ORDER BY a.attnum;
**************************

********* QUERY **********
SELECT c2.relname, i.indisprimary, i.indisunique, i.indisclustered,
i.indisvalid, pg_catalog.pg_get_indexdef(i.indexrelid, 0, true),
pg_catalog.pg_get_constraintdef(con.oid, true), contype,
condeferrable, condeferred, c2.reltablespace
FROM pg_catalog.pg_class c, pg_catalog.pg_class c2, pg_catalog.pg_index i
LEFT JOIN pg_catalog.pg_constraint con ON (conrelid = i.indrelid AND
conindid = i.indexrelid AND contype IN ('p','u','x'))
WHERE c.oid = '146989' AND c.oid = i.indrelid AND i.indexrelid = c2.oid
ORDER BY i.indisprimary DESC, i.indisunique DESC, c2.relname;
**************************

********* QUERY **********
SELECT conname,
pg_catalog.pg_get_constraintdef(r.oid, true) as condef
FROM pg_catalog.pg_constraint r
WHERE r.conrelid = '146989' AND r.contype = 'f' ORDER BY 1;
**************************

********* QUERY **********
SELECT conname, conrelid::pg_catalog.regclass,
pg_catalog.pg_get_constraintdef(c.oid, true) as condef
FROM pg_catalog.pg_constraint c
WHERE c.confrelid = '146989' AND c.contype = 'f' ORDER BY 1;
**************************

********* QUERY **********
SELECT t.tgname, pg_catalog.pg_get_triggerdef(t.oid, true), t.tgenabled
FROM pg_catalog.pg_trigger t
WHERE t.tgrelid = '146989' AND NOT t.tgisinternal
ORDER BY 1;
**************************

********* QUERY **********
SELECT c.oid::pg_catalog.regclass FROM pg_catalog.pg_class c,
pg_catalog.pg_inherits i WHERE c.oid=i.inhparent AND i.inhrelid =
'146989' ORDER BY inhseqno;
**************************

********* QUERY **********
SELECT c.oid::pg_catalog.regclass FROM pg_catalog.pg_class c,
pg_catalog.pg_inherits i WHERE c.oid=i.inhrelid AND i.inhparent =
'146989' ORDER BY c.oid::pg_catalog.regclass::pg_catalog.text;
**************************

Table "public.a1"
Column │ Type │ Modifiers
────────┼─────────┼───────────
id │ integer │ not null
v │ integer │
Indexes:
"a1_pkey" PRIMARY KEY, btree (id)
Referenced by:
TABLE "a2" CONSTRAINT "a2_id_fkey" FOREIGN KEY (id) REFERENCES a1(id)

postgres=# \d a2
********* 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 ~ '^(a2)$'
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, '', 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 = '146994';
**************************

********* 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
FROM pg_catalog.pg_attribute a
WHERE a.attrelid = '146994' AND a.attnum > 0 AND NOT a.attisdropped
ORDER BY a.attnum;
**************************

********* QUERY **********
SELECT conname,
pg_catalog.pg_get_constraintdef(r.oid, true) as condef
FROM pg_catalog.pg_constraint r
WHERE r.conrelid = '146994' AND r.contype = 'f' ORDER BY 1;
**************************

********* QUERY **********
SELECT conname, conrelid::pg_catalog.regclass,
pg_catalog.pg_get_constraintdef(c.oid, true) as condef
FROM pg_catalog.pg_constraint c
WHERE c.confrelid = '146994' AND c.contype = 'f' ORDER BY 1;
**************************

********* QUERY **********
SELECT t.tgname, pg_catalog.pg_get_triggerdef(t.oid, true), t.tgenabled
FROM pg_catalog.pg_trigger t
WHERE t.tgrelid = '146994' AND NOT t.tgisinternal
ORDER BY 1;
**************************

********* QUERY **********
SELECT c.oid::pg_catalog.regclass FROM pg_catalog.pg_class c,
pg_catalog.pg_inherits i WHERE c.oid=i.inhparent AND i.inhrelid =
'146994' ORDER BY inhseqno;
**************************

********* QUERY **********
SELECT c.oid::pg_catalog.regclass FROM pg_catalog.pg_class c,
pg_catalog.pg_inherits i WHERE c.oid=i.inhrelid AND i.inhparent =
'146994' ORDER BY c.oid::pg_catalog.regclass::pg_catalog.text;
**************************

Table "public.a2"
Column │ Type │ Modifiers
────────┼─────────┼───────────
id │ integer │
v │ integer │
Foreign-key constraints:
"a2_id_fkey" FOREIGN KEY (id) REFERENCES a1(id)

Regards

Pavel Stehule

> thanks
>
>
> J.V.
>
>
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