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Add OLD/NEW support to RETURNING in DML queries.

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This allows the RETURNING list of INSERT/UPDATE/DELETE/MERGE queries
to explicitly return old and new values by using the special aliases
"old" and "new", which are automatically added to the query (if not
already defined) while parsing its RETURNING list, allowing things
like:

  RETURNING old.colname, new.colname, ...

  RETURNING old.*, new.*

Additionally, a new syntax is supported, allowing the names "old" and
"new" to be changed to user-supplied alias names, e.g.:

  RETURNING WITH (OLD AS o, NEW AS n) o.colname, n.colname, ...

This is useful when the names "old" and "new" are already defined,
such as inside trigger functions, allowing backwards compatibility to
be maintained -- the interpretation of any existing queries that
happen to already refer to relations called "old" or "new", or use
those as aliases for other relations, is not changed.

For an INSERT, old values will generally be NULL, and for a DELETE,
new values will generally be NULL, but that may change for an INSERT
with an ON CONFLICT ... DO UPDATE clause, or if a query rewrite rule
changes the command type. Therefore, we put no restrictions on the use
of old and new in any DML queries.

Dean Rasheed, reviewed by Jian He and Jeff Davis.

Discussion: https://postgr.es/m/CAEZATCWx0J0-v=Qjc6gXzR=KtsdvAE7Ow=D=mu50AgOe+pvisQ@mail.gmail.com
This commit is contained in:
Dean Rasheed
2025-01-16 14:57:35 +00:00
parent 7407b2d48c
commit 80feb727c8
61 changed files with 2910 additions and 390 deletions
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4
src/interfaces/ecpg/preproc/parse.pl
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@@ -105,8 +105,8 @@ my %replace_line = (
'SHOW TRANSACTION ISOLATION LEVEL ecpg_into',
'VariableShowStmt SHOW SESSION AUTHORIZATION' =>
'SHOW SESSION AUTHORIZATION ecpg_into',
'returning_clause RETURNING target_list' =>
'RETURNING target_list opt_ecpg_into',
'returning_clause RETURNING returning_with_clause target_list' =>
'RETURNING returning_with_clause target_list opt_ecpg_into',
'ExecuteStmt EXECUTE name execute_param_clause' =>
'EXECUTE prepared_name execute_param_clause execute_rest',
'ExecuteStmt CREATE OptTemp TABLE create_as_target AS EXECUTE name execute_param_clause opt_with_data'