In 01e658fa74, the hash_func test
creates a type t1, but apparently a test running in parallel might
also use that name, depending on timing. Rename the type to avoid the
issue.
Add hash functions for the record type as well as a hash operator
family and operator class for the record type. This enables all the
hash functionality for the record type such as hash-based plans for
UNION/INTERSECT/EXCEPT DISTINCT, recursive queries using UNION
DISTINCT, hash joins, and hash partitioning.
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/flat/38eccd35-4e2d-6767-1b3c-dada1eac3124%402ndquadrant.com
- Test hashing of an array of a non-hashable element type.
- Test UNION [DISTINCT] with hash- and sort-based plans. (Previously,
only INTERSECT and EXCEPT where tested there.)
- Test UNION [DISTINCT] with a non-hashable column type. This
currently reverts to a sort-based plan even if enable_hashagg is on.
- Test UNION/INTERSECT/EXCEPT hash- and sort-based plans with arrays
as column types. Also test an array with a non-hashable element
type.
- Test UNION/INTERSECT/EXCEPT similarly with row types as column
types. Currently, this uses only sort-based plans because there is
no hashing support for row types.
- Add a test case that shows that recursive queries using UNION
[DISTINCT] require hashable column types.
- Add a currently failing test that uses UNION DISTINCT in a
cycle-detection use case using row types as column types.
Discussion: https://www.postgresql.org/message-id/flat/38eccd35-4e2d-6767-1b3c-dada1eac3124%402ndquadrant.com
This will be useful for hash partitioning, which needs a way to seed
the hash functions to avoid problems such as a hash index on a hash
partitioned table clumping all values into a small portion of the
bucket space; it's also useful for anything that wants a 64-bit hash
value rather than a 32-bit hash value.
Just in case somebody wants a 64-bit hash value that is compatible
with the existing 32-bit hash values, make the low 32-bits of the
64-bit hash value match the 32-bit hash value when the seed is 0.
Robert Haas and Amul Sul
Discussion: http://postgr.es/m/CA+Tgmoafx2yoJuhCQQOL5CocEi-w_uG4S2xT0EtgiJnPGcHW3g@mail.gmail.com
