Allow escaping of '?' using '??' in SQL expression

[pvarga88]

Using SQL operator, it is not possible to use '?' as a native operator (e.g. on Postgres). This PR is to allow using '??' as an escape mechanism, similar to the escaping mechanism used by Postgres JDBC.

This is to fix issue #836

[pvarga88]

Is there anything I need to do to have this looked at by maintainers? or just patience?

[rfelcman]

Could You please provide there examples of SQL (jsonb) query where ? is used as an operator?
Maybe JPA based example should be nice too?
These should be used as starting point for the tests which we want for functional changes.
I'm not sure if this code change related with Postgres is placed to the right area. It should be stored in Postgres platform area.
But I'm not sure if org.eclipse.persistence.internal.databaseaccess.Platform offers some API for this.
Some Postgres JSON features were introduced by #1389 .

[pvarga88]

The fix is not specific to Postgres, nor JSON, really. I just happen to run into this because Postgres uses '?' as an operator in many of its operators on JSONB:
https://www.postgresql.org/docs/11/functions-json.html

Oracle also uses '?' as an operator within its JSON_EXISTS
https://docs.oracle.com/en/database/oracle/oracle-database/21/adjsn/condition-JSON_EXISTS.html

As for an example, the following JPA query is not possible on Postgres without this fix:
SQL('?->stanza ?? ?', myentity.myjsonfield, :searchval")

↑ Note that I used two question marks where I want a literal question mark, rather than specifying a parameter in a parameterized query. This works with my proposed fix in this PR.

[rfelcman]

Please extend this PR with test. Good candidate where to put it into new method is
https://github.com/eclipse-ee4j/eclipselink/blob/master/jpa/eclipselink.jpa.test.jse/src/it/java/org/eclipse/persistence/jpa/json/TestJson.java

There is some example query against Oracle
SELECT je.value FROM jsonentity je WHERE json_exists(je.value, '$?(@.id == 1001)');

Example how to restrict test/code against some platform
https://github.com/eclipse-ee4j/eclipselink/blob/master/jpa/eclipselink.jpa.test.jse/src/it/java/org/eclipse/persistence/jpa/test/criteria/TestMathFunctions.java#L555
https://github.com/eclipse-ee4j/eclipselink/blob/master/jpa/eclipselink.jpa.test.jse/src/it/java/org/eclipse/persistence/jpa/test/criteria/TestDateTimeFunctions.java#L99

[pvarga88]

I'll give it a go but I don't have the full environment to test the tests so it may take a few trial and error commits.

[pvarga88]

Done. Test case added.

[rfelcman]

Please update copyright year in TestJson.java into
....Copyright (c) 2022, 2023....

[rfelcman]

LGTM

[pvarga88]

@rfelcman I would like to backport this to 4.0. Is there a policy or process for that or do I just submit a separate PR to the 4.0 branch?

[rfelcman]

@rfelcman I would like to backport this to 4.0. Is there a policy or process for that or do I just submit a separate PR to the 4.0 branch?

Just create new PR against 4.0 branch.

[pvarga88]

Thank you.
Created #2156