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MDL-53944 dml: make char2real() for mysql to support decimals

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- With the patch, 6 positions of scale accuracy are guaranteed
  per individual casted value.
- Backed with unit tests, both for varchar and clob.
- Added 2 missing tests about uses of the method with params
  and values.

Note: 6 was picked because looking to all databases implementation
postgres was found to be casting to real, aka, 6.
This commit is contained in:
Eloy Lafuente (stronk7) 2016-04-29 03:42:59 +02:00 • committed by Andrew Nicols
parent 440b4c54ca
commit 4ae653024d
2 changed files with 22 additions and 4 deletions
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6
lib/dml/mysqli_native_moodle_database.php
View file

@ -1504,7 +1504,11 @@ class mysqli_native_moodle_database extends moodle_database {
}
public function sql_cast_char2real($fieldname, $text=false) {
return ' CAST(' . $fieldname . ' AS DECIMAL) ';
// Set to 65 (max mysql 5.5 precision) with 7 as scale
// because we must ensure at least 6 decimal positions
// per casting given that postgres is casting to that scale (::real::).
// Can be raised easily but that must be done in all DBs and tests.
return ' CAST(' . $fieldname . ' AS DECIMAL(65,7)) ';
}
/**

20
lib/dml/tests/dml_test.php
View file

@ -3670,7 +3670,7 @@ class core_dml_testcase extends database_driver_testcase {
$DB->insert_record($tablename, array('name'=>'10.10', 'nametext'=>'10.10', 'res'=>5.1));
$DB->insert_record($tablename, array('name'=>'91.10', 'nametext'=>'91.10', 'res'=>666));
$DB->insert_record($tablename, array('name'=>'011.10', 'nametext'=>'011.10', 'res'=>10.1));
$DB->insert_record($tablename, array('name'=>'011.13333333', 'nametext'=>'011.13333333', 'res'=>10.1));
// Casting varchar field.
$sql = "SELECT * FROM {{$tablename}} WHERE ".$DB->sql_cast_char2real('name')." > res";
@ -3681,8 +3681,11 @@ class core_dml_testcase extends database_driver_testcase {
$records = $DB->get_records_sql($sql);
$this->assertCount(3, $records);
$this->assertSame('10.10', reset($records)->name);
$this->assertSame('011.10', next($records)->name);
$this->assertSame('011.13333333', next($records)->name);
$this->assertSame('91.10', next($records)->name);
// And verify we can operate with them without too much problem with at least 6 decimals scale accuracy.
$sql = "SELECT AVG(" . $DB->sql_cast_char2real('name') . ") FROM {{$tablename}}";
$this->assertEquals(37.44444443333333, (float)$DB->get_field_sql($sql), '', 1.0E-6);
// Casting text field.
$sql = "SELECT * FROM {{$tablename}} WHERE ".$DB->sql_cast_char2real('nametext', true)." > res";
@ -3693,8 +3696,19 @@ class core_dml_testcase extends database_driver_testcase {
$records = $DB->get_records_sql($sql);
$this->assertCount(3, $records);
$this->assertSame('10.10', reset($records)->nametext);
$this->assertSame('011.10', next($records)->nametext);
$this->assertSame('011.13333333', next($records)->nametext);
$this->assertSame('91.10', next($records)->nametext);
// And verify we can operate with them without too much problem with at least 6 decimals scale accuracy.
$sql = "SELECT AVG(" . $DB->sql_cast_char2real('nametext', true) . ") FROM {{$tablename}}";
$this->assertEquals(37.44444443333333, (float)$DB->get_field_sql($sql), '', 1.0E-6);
// Check it works with values passed as param.
$sql = "SELECT name FROM {{$tablename}} WHERE FLOOR(res - " . $DB->sql_cast_char2real(':param') . ") = 0";
$this->assertEquals('011.13333333', $DB->get_field_sql($sql, array('param' => '10.09999')));
// And also, although not recommended, with directly passed values.
$sql = "SELECT name FROM {{$tablename}} WHERE FLOOR(res - " . $DB->sql_cast_char2real('10.09999') . ") = 0";
$this->assertEquals('011.13333333', $DB->get_field_sql($sql));
}
public function test_sql_compare_text() {