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MDL-58593 database: More efficiently track issued key names

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This commit is contained in:
Eric Merrill 2017-04-13 12:21:13 -04:00
parent 0714bcb2a2
commit cd729dc905
2 changed files with 51 additions and 7 deletions
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26
lib/ddl/sql_generator.php
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@ -1074,8 +1074,11 @@ abstract class sql_generator {
// along all the request life, but never to return cached results
// We need this because sql statements are created before executing
// them, hence names doesn't exist "physically" yet in DB, so we need
// to known which ones have been used
static $used_names = array();
// to known which ones have been used.
// We track all the keys used, and the previous counters to make subsequent creates faster.
// This may happen a lot with things like bulk backups or restores.
static $usednames = array();
static $previouscounters = array();
// Use standard naming. See http://docs.moodle.org/en/XMLDB_key_and_index_naming
$tablearr = explode ('_', $tablename);
@ -1094,17 +1097,26 @@ abstract class sql_generator {
$maxlengthwithoutsuffix = $this->names_max_length - strlen($suffix) - ($suffix ? 1 : 0);
$namewithsuffix = substr($name, 0, $maxlengthwithoutsuffix) . ($suffix ? ('_' . $suffix) : '');
// If the calculated name is in the cache, or if we detect it by introspecting the DB let's modify if
$counter = 1;
while (in_array($namewithsuffix, $used_names) || $this->isNameInUse($namewithsuffix, $suffix, $tablename)) {
if (isset($previouscounters[$name])) {
// If we have a counter stored, we will need to modify the key to the next counter location.
$counter = $previouscounters[$name] + 1;
$namewithsuffix = substr($name, 0, $maxlengthwithoutsuffix - strlen($counter)) .
$counter . ($suffix ? ('_' . $suffix) : '');
} else {
$counter = 1;
}
// If the calculated name is in the cache, or if we detect it by introspecting the DB let's modify it.
while (isset($usednames[$namewithsuffix]) || $this->isNameInUse($namewithsuffix, $suffix, $tablename)) {
// Now iterate until not used name is found, incrementing the counter
$counter++;
$namewithsuffix = substr($name, 0, $maxlengthwithoutsuffix - strlen($counter)) .
$counter . ($suffix ? ('_' . $suffix) : '');
}
// Add the name to the cache
$used_names[] = $namewithsuffix;
// Add the name to the cache. Using key look with isset because it is much faster than in_array.
$usednames[$namewithsuffix] = true;
$previouscounters[$name] = $counter;
// Quote it if necessary (reserved words)
$namewithsuffix = $this->getEncQuoted($namewithsuffix);

32
lib/ddl/tests/ddl_test.php
View File

@ -2080,6 +2080,38 @@ class core_ddl_testcase extends database_driver_testcase {
strlen($gen->getNameForObject($table, $fields, $suffix)),
'Generated object name is too long. $i = '.$i);
}
// Now test to confirm that a duplicate name isn't issued, even if they come from different root names.
// Move to a new field.
$fields = "fl";
// Insert twice, moving is to a key with fl2.
$this->assertEquals($gen->names_max_length - 1, strlen($gen->getNameForObject($table, $fields, $suffix)));
$result1 = $gen->getNameForObject($table, $fields, $suffix);
// Make sure we end up with _fl2_ in the result.
$this->assertRegExp('/_fl2_/', $result1);
// Now, use a field that would result in the same key if it wasn't already taken.
$fields = "fl2";
// Because we are now at the max key length, it will try:
// - _fl2_ (the natural name)
// - _fl2_ (removing the original 2, and adding a counter 2)
// - then settle on _fl3_.
$result2 = $gen->getNameForObject($table, $fields, $suffix);
$this->assertRegExp('/_fl3_/', $result2);
// Make sure they don't match.
$this->assertNotEquals($result1, $result2);
// But are only different in the way we expect. This confirms the test is working properly.
$this->assertEquals(str_replace('_fl2_', '', $result1), str_replace('_fl3_', '', $result2));
// Now go back. We would expect the next result to be fl3 again, but it is taken, so it should move to fl4.
$fields = "fl";
$result3 = $gen->getNameForObject($table, $fields, $suffix);
$this->assertNotEquals($result2, $result3);
$this->assertRegExp('/_fl4_/', $result3);
}
}