Add ROW() record constructor support
#1451
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This isn't the right direction to head in. There isn't a tuple type in Postgres.
SELECT * FROM pg_type ORDER BY typname;The ROW() expression works with composite and anonymous RECORD types, as described in the documentation here:
https://www.postgresql.org/docs/15/sql-expressions.html#SQL-SYNTAX-ROW-CONSTRUCTORS
With types, we are adhering to Postgres' documentation as close as possible. All of the functions for each type (bpcharin, timestamp_recv, etc.) are functions that exist within Postgres, and for those you can find them in pg_type. The comparison functions (int4gt, etc.) exist in the pg_operator table:
SELECT
o.oprname,
src_typ.typname AS oprleft,
tgt_typ.typname AS oprright,
res_typ.typname AS oprresult,
o.oprcode::varchar
FROM
pg_operator o
JOIN
pg_catalog.pg_type src_typ ON o.oprleft = src_typ.oid
JOIN
pg_catalog.pg_type tgt_typ ON o.oprright = tgt_typ.oid
JOIN
pg_catalog.pg_type res_typ ON o.oprresult = res_typ.oid
WHERE
o.oprname = '>'
ORDER BY
src_typ.typname, tgt_typ.typname;The best way to proceed would be to add support for composite types, and then follow that up with RECORD types (which you may remember seeing a taste of it in my triggers PR, which added enough of RECORD to work with the OLD and NEW values in trigger functions).
I've thought about how to properly implement RECORD types for a little bit (mainly while implementing triggers), and one potential idea for anonymous record types would be to have the row and types combined into a single value. So it would look something like:
type RecordValue struct {
Value sql.Row
Types []id.Type
}This works on the assumption that an array of anonymous RECORD values could each have a different row representation, but that may not be true (would need to follow that up with a bit of reading).
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ROW() supportROW() record constructor support
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@Hydrocharged – |
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This is definitely a step in the right direction, but there are some details that we need to nail down before we can merge this in. For example, right now comparisons are done by directly comparing the values. My hunch would be that they use the comparison functions for the appropriate types, which would need the type information available at that point. When you're back next week, we can hop on a quick call and go over a few more details. |
Initial support for the
ROW()constructor expression, which creates anonymous records.This PR adds support for basic uses of the
ROW()constructor, such as creating records from groups of expressions, selecting records, comparing records, and using records inWHEREclauses. There are still severalrecordfeatures that don't work yet, such as using a table alias with theROW()constructor.Fixes: #1425