Fix convert_tz function in Postgresql

[mesolaries]

$toTz parameter was passed before $fromTz. It causes convert_tz function to work not as expected. This pr fixes this bug.

[mesolaries]

@x86demon please review

[paulferrett]

@x86demon This issue tripped me up for quite a while as well.

[x86demon]

@mesolaries thank you for your PR and fix.
Please update tests to show the bug and correctness of the fix.

Sorry for delay in the answer.

[x86demon]

I've checked CONVERT_TZ and it works as expected.
As a source of this implementation MySQL CONVERT_TZ was taken. https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html#function_convert-tz
DQL function should return same results for both supported platforms (MySQL and PostgreSQL)
I've used next example
MySQL

mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','UTC','Europe/Kiev');
+-------------------------------------------------------+
| CONVERT_TZ('2004-01-01 12:00:00','UTC','Europe/Kiev') |
+-------------------------------------------------------+
| 2004-01-01 14:00:00                                   |
+-------------------------------------------------------+

Current implementation for PostgreSQL

postgres=# SELECT "timestamp"('2004-01-01 12:00:00' AT TIME ZONE 'Europe/Kiev' AT TIME ZONE 'UTC');
      timestamp      
---------------------
 2004-01-01 14:00:00

I'm closing the PR

@mesolaries, @paulferrett thank you for paying attention.

[mesolaries]

@x86demon Your example is not the same as current PostgreSQL implementation. Parenthesis are in wrong place.
Your example: SELECT "timestamp"('2004-01-01 12:00:00' AT TIME ZONE 'Europe/Kiev' AT TIME ZONE 'UTC');
Actual implementation: SELECT "timestamp"('2004-01-01 12:00:00') AT TIME ZONE 'Europe/Kiev' AT TIME ZONE 'UTC';

doctrine-extensions/src/Oro/ORM/Query/AST/Platform/Functions/Postgresql/ConvertTz.php

Lines 22 to 24 in 67eda39

	return '"timestamp"('
	. $this->getExpressionValue($value, $sqlWalker)
	. ')'

So, let's assume I want to convert datetime from UTC timezone to Europe/Kiev timezone. I will take current implementation as example. Expected output: 2004-01-01T14:00:00.000Z

postgres=# SELECT "timestamp"('2004-01-01 12:00:00') AT TIME ZONE 'Europe/Kiev' AT TIME ZONE 'UTC';
      timestamp      
---------------------
2004-01-01T10:00:00.000Z

As you can see the output is wrong. This is because $fromTz parameter is passed after $toTz as I mentioned before.

[x86demon]

@mesolaries you are right, I've missed parentheses position.
Please update test so I'll be able to merge the PR

[x86demon]

Please, check expectedResult. Query changed but result is still the same.

[mesolaries]

t0_.created_at is 2014-01-04 05:06:07. When converting from +00:00 to +01:00 expected result should be 2014-01-04 06:06:07

[x86demon]

I have applied your changes and run tests. Here is an output:

1) Oro\Tests\ORM\AST\Query\Functions\FunctionsTest::testDqlFunction with data set #26 (array(array('convert_tz', 'Oro\ORM\Query\AST\Functions\D...vertTz', 'datetime')), 'SELECT CONVERT_TZ(f.createdAt...id = 1', 'SELECT "timestamp"(t0_.create...id = 1', array('2014-01-04 06:06:07'))
Unexpected result for "SELECT CONVERT_TZ(f.createdAt, '+00:00', '+01:00') FROM Oro\Entities\Foo f WHERE f.id = 1"
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    0 => '2014-01-04 06:06:07'
+    0 => '2014-01-04 04:06:07'
 )

/var/www/projects/oro-dev/doctrine-extensions/tests/Oro/Tests/ORM/AST/Query/Functions/FunctionsTest.php:48

2) Oro\Tests\ORM\AST\Query\Functions\FunctionsTest::testDqlFunction with data set #27 (array(array('convert_tz', 'Oro\ORM\Query\AST\Functions\D...vertTz', 'datetime')), 'SELECT CONVERT_TZ('2014-01-01...id = 1', 'SELECT "timestamp"('2014-01-0...id = 1', array('2014-01-01 01:00:00'))
Unexpected result for "SELECT CONVERT_TZ('2014-01-01 00:00:00', '+00:00', '+01:00') FROM Oro\Entities\Foo f WHERE f.id = 1"
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    0 => '2014-01-01 01:00:00'
+    0 => '2013-12-31 23:00:00'
 )

/var/www/projects/oro-dev/doctrine-extensions/tests/Oro/Tests/ORM/AST/Query/Functions/FunctionsTest.php:48

3) Oro\Tests\ORM\AST\Query\Functions\FunctionsTest::testDqlFunction with data set #29 (array(array('convert_tz', 'Oro\ORM\Query\AST\Functions\D...vertTz', 'datetime')), 'SELECT CONVERT_TZ('2014-01-01...id = 1', 'SELECT "timestamp"('2014-01-0...id = 1', array('2014-01-01 02:00:00'))
Unexpected result for "SELECT CONVERT_TZ('2014-01-01 00:00:00', '+01:00', '+03:00') FROM Oro\Entities\Foo f WHERE f.id = 1"
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
 Array (
-    0 => '2014-01-01 02:00:00'
+    0 => '2013-12-31 22:00:00'
 )

You may check MySQL version of tests. DQL and expectedResult must be the same for MySQL and PostgreSQL and tests should pass.
Check .travis.yml for details on how to execute tests for this project

[mesolaries]

The problem is in timezone confusion. AT TIME ZONE supports timezones in POSIX style

https://github.com/eggert/tz/blob/2018g/etcetera#L38-L44

I suggest to replace '+xx:00' type timezones to locality based timezone 'UTC', 'Europe/Kiev' for example.
Thus, the tests will be passed and less confusing.

[x86demon]

I'm ok with such change in tests if these changes will be applied for both DBs and will show that translated SQL produces same results for a given DQL.
Is +01:00 behaves differently for MySQL and PostgreSQL? If so CONVERT_TZ should have logic to prevent confusion (may be added as a separate issue)

[mesolaries]

Yes, +01:00 behaves differently. I will add necessary tests.

[x86demon]

Please, do not forget about DST and issues it may bring to tests in different periods of year