Deallocate prepared statements

[fpoy]

Fixes #1256

Description

Implement a common method in each database connector to destroy the prepared query when we're done with it

Cf Issue #1256 : TODO Deallocate prepared statements

To closes a prepared statement :

• MySQLi have mysqli_stmt_close()
  https://www.php.net/manual/en/mysqli-stmt.close.php
• OCI8 have oci_free_statement()
  https://www.php.net/manual/en/function.oci-free-statement.php
• Postgre does not have a specific PHP function for deleting a prepared statement,
  the SQL DEALLOCATE statement can be used for that purpose :
  https://www.php.net/manual/en/function.pg-prepare.php
  https://www.postgresql.org/docs/8.1/sql-deallocate.html
• SQLite3 have SQLite3Stmt::close()
  https://www.php.net/manual/en/sqlite3stmt.close.php
• SQLSRV have sqlsrv_free_stmt()
  https://www.php.net/manual/en/function.sqlsrv-free-stmt.php

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[kenjis]

Thank you for contribution!

This is not a bug fix, so this should go to 4.3 branch.
See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#if-you-sent-to-the-wrong-branch

[fpoy]

@kenjis that's done, I've rebased the PR to 4.3 branch

[kenjis]

@fpoy There are four commits made by Paul and me. Please drop them.
You can do it with git rebase.
See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#updating-your-branch

[fpoy]

@fpoy There are four commits made by Paul and me. Please drop them. You can do it with git rebase. See https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#updating-your-branch

@kenjis it's done, there are only my commits left on the branch...

[kenjis]

Thank you. The commits are okay.

1. We need the documentation. Please add changelog.
2. If possible, please reduce rather than increase phpstan-baseline.neon.dist.

[fpoy]

The documentation on this subject already exists
What should be added to it ?

[fpoy]

in user_guide_src/source/database/queries/020.php

$error = $pQuery->close();

Would that be sufficient ?

[kenjis]

Please add about this enhancement in the Enhancements section:
https://github.com/codeigniter4/CodeIgniter4/blob/4.3/user_guide_src/source/changelogs/v4.3.0.rst#database

[MGatner]

Thanks @fpoy this looks like great stuff! @kenjis has already covered most of it but summoning the rest of the @codeigniter4/database-team so they can see this too.

[kenjis]

The documentation on this subject already exists
What should be added to it ?

https://codeigniter4.github.io/CodeIgniter4/database/queries.html#close

It seems the close() method does nothing with some DBMS before this PR.
How about adding the note for it?
Something like this:

Since v4.3.0, the close() method deallocates the prepared query in all DBMS. In previous versions, the prepared query was not deallocated in xxx and xxx.

[sclubricants]

LGMT

The only thing is you might add to the test to check that the statement is actually cleared. For MySQL:

SHOW GLOBAL STATUS LIKE '%prepared_stmt_count%';
# 0

SQLITE https://www.sqlite.org/c3ref/stmt_status.html

Postgres https://www.postgresql.org/docs/current/view-pg-prepared-statements.html

[MGatner]

This is looking great everyone. Thanks for all the collaboration!

[MGatner]

Looks great! I can't tell if that last thread is resolved yet.

Whoever merges: please squash this one.