Support WITH queries (common table expressions) #11757
Description
Use case:
Using asyncpg to select string arrays.
A query like SELECT * FROM tbl results in a type-lookup query like the following if the table contains arrays of type string:
Concrete use-case was using cr8 insert-from-sql to copy data. Under the hood it uses asyncpg with the following code to retrieve the schema of the select query and to generate the insert statement:
conn = await asyncpg.connect(src_uri)
try:
stmt = await conn.prepare(query)
insert = mk_insert(table, stmt.get_attributes())WITH RECURSIVE typeinfo_tree(
oid, ns, name, kind, basetype, elemtype, elemdelim,
range_subtype, attrtypoids, attrnames, depth)
AS (
SELECT
ti.oid, ti.ns, ti.name, ti.kind, ti.basetype,
ti.elemtype, ti.elemdelim, ti.range_subtype,
ti.attrtypoids, ti.attrnames, 0
FROM
(
SELECT
t.oid AS oid,
ns.nspname AS ns,
t.typname AS name,
t.typtype AS kind,
(CASE WHEN t.typtype = 'd' THEN
(WITH RECURSIVE typebases(oid, depth) AS (
SELECT
t2.typbasetype AS oid,
0 AS depth
FROM
pg_type t2
WHERE
t2.oid = t.oid
UNION ALL
SELECT
t2.typbasetype AS oid,
tb.depth + 1 AS depth
FROM
pg_type t2,
typebases tb
WHERE
tb.oid = t2.oid
AND t2.typbasetype != 0
) SELECT oid FROM typebases ORDER BY depth DESC LIMIT 1)
ELSE NULL
END) AS basetype,
t.typelem AS elemtype,
elem_t.typdelim AS elemdelim,
range_t.rngsubtype AS range_subtype,
(CASE WHEN t.typtype = 'c' THEN
(SELECT
array_agg(ia.atttypid ORDER BY ia.attnum)
FROM
pg_attribute ia
INNER JOIN pg_class c
ON (ia.attrelid = c.oid)
WHERE
ia.attnum > 0 AND NOT ia.attisdropped
AND c.reltype = t.oid)
ELSE NULL
END) AS attrtypoids,
(CASE WHEN t.typtype = 'c' THEN
(SELECT
array_agg(ia.attname::text ORDER BY ia.attnum)
FROM
pg_attribute ia
INNER JOIN pg_class c
ON (ia.attrelid = c.oid)
WHERE
ia.attnum > 0 AND NOT ia.attisdropped
AND c.reltype = t.oid)
ELSE NULL
END) AS attrnames
FROM
pg_catalog.pg_type AS t
INNER JOIN pg_catalog.pg_namespace ns ON (
ns.oid = t.typnamespace)
LEFT JOIN pg_type elem_t ON (
t.typlen = -1 AND
t.typelem != 0 AND
t.typelem = elem_t.oid
)
LEFT JOIN pg_range range_t ON (
t.oid = range_t.rngtypid
)
)
AS ti
WHERE
ti.oid = any($1::oid[])
UNION ALL
SELECT
ti.oid, ti.ns, ti.name, ti.kind, ti.basetype,
ti.elemtype, ti.elemdelim, ti.range_subtype,
ti.attrtypoids, ti.attrnames, tt.depth + 1
FROM
(
SELECT
t.oid AS oid,
ns.nspname AS ns,
t.typname AS name,
t.typtype AS kind,
(CASE WHEN t.typtype = 'd' THEN
(WITH RECURSIVE typebases(oid, depth) AS (
SELECT
t2.typbasetype AS oid,
0 AS depth
FROM
pg_type t2
WHERE
t2.oid = t.oid
UNION ALL
SELECT
t2.typbasetype AS oid,
tb.depth + 1 AS depth
FROM
pg_type t2,
typebases tb
WHERE
tb.oid = t2.oid
AND t2.typbasetype != 0
) SELECT oid FROM typebases ORDER BY depth DESC LIMIT 1)
ELSE NULL
END) AS basetype,
t.typelem AS elemtype,
elem_t.typdelim AS elemdelim,
range_t.rngsubtype AS range_subtype,
(CASE WHEN t.typtype = 'c' THEN
(SELECT
array_agg(ia.atttypid ORDER BY ia.attnum)
FROM
pg_attribute ia
INNER JOIN pg_class c
ON (ia.attrelid = c.oid)
WHERE
ia.attnum > 0 AND NOT ia.attisdropped
AND c.reltype = t.oid)
ELSE NULL
END) AS attrtypoids,
(CASE WHEN t.typtype = 'c' THEN
(SELECT
array_agg(ia.attname::text ORDER BY ia.attnum)
FROM
pg_attribute ia
INNER JOIN pg_class c
ON (ia.attrelid = c.oid)
WHERE
ia.attnum > 0 AND NOT ia.attisdropped
AND c.reltype = t.oid)
ELSE NULL
END) AS attrnames
FROM
pg_catalog.pg_type AS t
INNER JOIN pg_catalog.pg_namespace ns ON (
ns.oid = t.typnamespace)
LEFT JOIN pg_type elem_t ON (
t.typlen = -1 AND
t.typelem != 0 AND
t.typelem = elem_t.oid
)
LEFT JOIN pg_range range_t ON (
t.oid = range_t.rngtypid
)
)
ti,
typeinfo_tree tt
WHERE
(tt.elemtype IS NOT NULL AND ti.oid = tt.elemtype)
OR (tt.attrtypoids IS NOT NULL AND ti.oid = any(tt.attrtypoids))
OR (tt.range_subtype IS NOT NULL AND ti.oid = tt.range_subtype)
)
SELECT DISTINCT
*,
basetype::regtype::text AS basetype_name,
elemtype::regtype::text AS elemtype_name,
range_subtype::regtype::text AS range_subtype_name
FROM
typeinfo_tree
ORDER BY
depth DESCFeature description:
WITH common table expressions as described in the PostgreSQL documentation: https://www.postgresql.org/docs/current/queries-with.html
Out of Scope
- Recursive with. (Estimate was for non-recursive). We can follow up on this afterwards
- DML operations within WITH
- Materialized WITH.