Hi so 28. 8. 2021 v 11:57 odesÃlatel Gilles Darold <gil...@darold.net> napsal:
> Hi, > > Review resume: > > > This patch implements Schema Variables that are database objects that can > hold a single or composite value following the data type used at variable > declaration. Schema variables, like relations, exist within a schema and > their access is controlled via GRANT and REVOKE commands. The schema > variable can be created by the CREATE VARIABLE command, altered using ALTER > VARIABLE and removed using DROP VARIABLE. > > The value of a schema variable is local to the current session. Retrieving > a variable's value returns either a NULL or a default value, unless its > value is set to something else in the current session with a LET command. > The content of a variable is not transactional. This is the same as in > regular variables in PL languages. > > Schema variables are retrieved by the SELECT SQL command. Their value is > set with the LET SQL command. While schema variables share properties with > tables, their value cannot be updated with an UPDATE command. > > The patch apply with the patch command without problem and compilation > reports no warning or errors. Regression tests pass successfully using make > check or make installcheck > It also includes all documentation and regression tests. > > Performances are near the set of plpgsql variable settings which is > impressive: > > do $$ > declare var1 int ; i int; > begin > for i in 1..1000000 > loop > var1 := i; > end loop; > end; > $$; > DO > Time: 71,515 ms > > CREATE VARIABLE var1 AS integer; > do $$ > declare i int ; > begin > for i in 1..1000000 > loop > let var1 = i; > end loop; > end; > $$; > DO > Time: 94,658 ms > > There is just one thing that puzzles me. We can use : > > CREATE VARIABLE var1 AS date NOT NULL; > postgres=# SELECT var1; > ERROR: null value is not allowed for NOT NULL schema variable "var1" > > which I understand and is the right behavior. But if we use: > > CREATE IMMUTABLE VARIABLE var1 AS date NOT NULL; > postgres=# SELECT var1; > ERROR: null value is not allowed for NOT NULL schema variable "var1" > DETAIL: The schema variable was not initialized yet. > postgres=# LET var1=current_date; > ERROR: schema variable "var1" is declared IMMUTABLE > > It should probably be better to not allow NOT NULL when IMMUTABLE is used > because the variable can not be used at all. Also probably IMMUTABLE > without a DEFAULT value should also be restricted as it makes no sens. If > the user wants the variable to be NULL he must use DEFAULT NULL. This is > just a though, the above error messages are explicit and the user can > understand what wrong declaration he have done. > I wrote a check that disables this case. Please, see the attached patch. I agree, so this case is confusing, and it is better to disable it. Regards Pavel > Except that I think this patch is ready for committers, so if there is no > other opinion in favor of restricting the use of IMMUTABLE with NOT NULL > and DEFAULT I will change the status to ready for committers. > > -- > Gilles Daroldhttp://www.darold.net/ > >
schema-variables-20210908.patch.gz
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