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Tom Lane 0da39aa766 Handle default NULL insertion a little better. ... If a column is omitted in an INSERT, and there's no column default, the code in preptlist.c generates a NULL Const to be inserted. Furthermore, if the column is of a domain type, we wrap the Const in CoerceToDomain, so as to throw a run-time error if the domain has a NOT NULL constraint. That's fine as far as it goes, but there are two problems: 1. We're being sloppy about the type/typmod that the Const is labeled with. It really should have the domain's base type/typmod, since it's the input to CoerceToDomain not the output. This can result in coerce_to_domain inserting a useless length-coercion function (useless because it's being applied to a null). The coercion would typically get const-folded away later, but it'd be better not to create it in the first place. 2. We're not applying expression preprocessing (specifically, eval_const_expressions) to the resulting expression tree. The planner's primary expression-preprocessing pass already happened, so that means the length coercion step and CoerceToDomain node miss preprocessing altogether. This is at the least inefficient, since it means the length coercion and CoerceToDomain will actually be executed for each inserted row, though they could be const-folded away in most cases. Worse, it seems possible that missing preprocessing for the length coercion could result in an invalid plan (for example, due to failing to perform default-function-argument insertion). I'm not aware of any live bug of that sort with core datatypes, and it might be unreachable for extension types as well because of restrictions of CREATE CAST, but I'm not entirely convinced that it's unreachable. Hence, it seems worth back-patching the fix (although I only went back to v14, as the patch doesn't apply cleanly at all in v13). There are several places in the rewriter that are building null domain constants the same way as preptlist.c. While those are before the planner and hence don't have any reachable bug, they're still applying a length coercion that will be const-folded away later, uselessly wasting cycles. Hence, make a utility routine that all of these places can call to do it right. Making this code more careful about the typmod assigned to the generated NULL constant has visible but cosmetic effects on some of the plans shown in contrib/postgres_fdw's regression tests. Discussion: https://postgr.es/m/1865579.1738113656@sss.pgh.pa.us Backpatch-through: 14		5 months ago
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expected	Handle default NULL insertion a little better.	5 months ago
sql	Add OLD/NEW support to RETURNING in DML queries.	5 months ago
t	postgres_fdw: SCRAM authentication pass-through	6 months ago
.gitignore	Add postgres_fdw contrib module.	13 years ago
Makefile	postgres_fdw: SCRAM authentication pass-through	6 months ago
connection.c	Check return of pg_b64_encode() for error	5 months ago
deparse.c	Update copyright for 2025	6 months ago
meson.build	postgres_fdw: SCRAM authentication pass-through	6 months ago
option.c	postgres_fdw: SCRAM authentication pass-through	6 months ago
postgres_fdw--1.0--1.1.sql	postgres_fdw: Add functions to discard cached connections.	4 years ago
postgres_fdw--1.0.sql	Add postgres_fdw contrib module.	13 years ago
postgres_fdw--1.1--1.2.sql	postgres_fdw: Extend postgres_fdw_get_connections to return user name.	9 months ago
postgres_fdw.c	Update copyright for 2025	6 months ago
postgres_fdw.control	postgres_fdw: Add "used_in_xact" column to postgres_fdw_get_connections().	11 months ago
postgres_fdw.h	Update copyright for 2025	6 months ago
shippable.c	Update copyright for 2025	6 months ago