Duplicate code is one of the most pungent code smells. A rule that is often used is to re-structure code once it is duplicated in three or more places.
Common duplication problems, and corresponding solutions are:
Complex classes like MSSQLSchemaManager often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use MSSQLSchemaManager, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 11 | class MSSQLSchemaManager extends DBSchemaManager  | 
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| 12 | { | 
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| 13 | |||
| 14 | /**  | 
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| 15 | * Stores per-request cached constraint checks that come from the database.  | 
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| 16 | *  | 
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| 17 | * @var array  | 
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| 18 | */  | 
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| 19 | protected static $cached_checks = [];  | 
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| 20 | |||
| 21 | /**  | 
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| 22 | * Builds the internal MS SQL Server index name given the silverstripe table and index name  | 
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| 23 | *  | 
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| 24 | * @param string $tableName  | 
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| 25 | * @param string $indexName  | 
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| 26 | * @param string $prefix The optional prefix for the index. Defaults to "ix" for indexes.  | 
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| 27 | * @return string The name of the index  | 
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| 28 | */  | 
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| 29 | public function buildMSSQLIndexName($tableName, $indexName, $prefix = 'ix')  | 
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| 36 | |||
| 37 | |||
| 38 | /**  | 
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| 39 | * This will set up the full text search capabilities.  | 
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| 40 | *  | 
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| 41 | * @param string $name Name of full text catalog to use  | 
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| 42 | */  | 
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| 43 | public function createFullTextCatalog($name = 'ftCatalog')  | 
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| 50 | |||
| 51 | /**  | 
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| 52 | * Check that a fulltext catalog has been created yet.  | 
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| 53 | *  | 
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| 54 | * @param string $name Name of full text catalog to use  | 
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| 55 | * @return boolean  | 
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| 56 | */  | 
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| 57 | public function fullTextCatalogExists($name = 'ftCatalog')  | 
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| 64 | |||
| 65 | /**  | 
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| 66 | * Sleep until the catalog has been fully rebuilt. This is a busy wait designed for situations  | 
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| 67 | * when you need to be sure the index is up to date - for example in unit tests.  | 
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| 68 | *  | 
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| 69 | * TODO: move this to Database class? Can we assume this will be useful for all databases?  | 
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| 70 | * Also see the wrapper functions "waitUntilIndexingFinished" in SearchFormTest and TranslatableSearchFormTest  | 
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| 71 | *  | 
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| 72 | * @param int $maxWaitingTime Time in seconds to wait for the database.  | 
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| 73 | */  | 
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| 74 | public function waitUntilIndexingFinished($maxWaitingTime = 15)  | 
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| 94 | |||
| 95 | /**  | 
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| 96 | * Check if a fulltext index exists on a particular table name.  | 
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| 97 | *  | 
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| 98 | * @param string $tableName  | 
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| 99 | * @return boolean TRUE index exists | FALSE index does not exist | NULL no support  | 
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| 100 | */  | 
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| 101 | public function fulltextIndexExists($tableName)  | 
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| 115 | |||
| 116 | /**  | 
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| 117 | * MSSQL stores the primary key column with an internal identifier,  | 
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| 118 | * so a lookup needs to be done to determine it.  | 
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| 119 | *  | 
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| 120 | * @param string $tableName Name of table with primary key column "ID"  | 
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| 121 | * @return string Internal identifier for primary key  | 
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| 122 | */  | 
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| 123 | public function getPrimaryKey($tableName)  | 
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| 136 | |||
| 137 | public function createDatabase($name)  | 
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| 141 | |||
| 142 | public function dropDatabase($name)  | 
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| 146 | |||
| 147 | public function databaseExists($name)  | 
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| 158 | |||
| 159 | public function databaseList()  | 
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| 163 | |||
| 164 | /**  | 
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| 165 | * Create a new table.  | 
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| 166 | *  | 
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| 167 | * @param string $tableName The name of the table  | 
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| 168 | * @param array $fields A map of field names to field types  | 
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| 169 | * @param array $indexes A map of indexes  | 
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| 170 | * @param array $options An map of additional options. The available keys are as follows:  | 
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| 171 | * - 'MSSQLDatabase'/'MySQLDatabase'/'PostgreSQLDatabase' - database-specific options such as "engine" for MySQL.  | 
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| 172 | * - 'temporary' - If true, then a temporary table will be created  | 
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| 173 | * @param array $advancedOptions  | 
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| 174 | * @return string The table name generated. This may be different from the table name, for example with temporary tables.  | 
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| 175 | */  | 
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| 176 | public function createTable($tableName, $fields = null, $indexes = null, $options = null, $advancedOptions = null)  | 
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| 213 | |||
| 214 | /**  | 
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| 215 | * Alter a table's schema.  | 
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| 216 | * @param string $tableName The name of the table to alter  | 
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| 217 | * @param array $newFields New fields, a map of field name => field schema  | 
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| 218 | * @param array $newIndexes New indexes, a map of index name => index type  | 
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| 219 | * @param array $alteredFields Updated fields, a map of field name => field schema  | 
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| 220 | * @param array $alteredIndexes Updated indexes, a map of index name => index type  | 
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| 221 | * @param array $alteredOptions  | 
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| 222 | * @param array $advancedOptions  | 
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| 223 | */  | 
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| 224 | public function alterTable($tableName, $newFields = null, $newIndexes = null, $alteredFields = null, $alteredIndexes = null, $alteredOptions=null, $advancedOptions=null)  | 
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| 265 | |||
| 266 | /**  | 
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| 267 | * Given the table and column name, retrieve the constraint name for that column  | 
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| 268 | * in the table.  | 
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| 269 | *  | 
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| 270 | * @param string $tableName Table name column resides in  | 
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| 271 | * @param string $columnName Column name the constraint is for  | 
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| 272 | * @return string|null  | 
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| 273 | */  | 
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| 274 | public function getConstraintName($tableName, $columnName)  | 
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| 283 | |||
| 284 | /**  | 
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| 285 | * Given a table and column name, return a check constraint clause for that column in  | 
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| 286 | * the table.  | 
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| 287 | *  | 
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| 288 | * This is an expensive query, so it is cached per-request and stored by table. The initial  | 
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| 289 | * call for a table that has not been cached will query all columns and store that  | 
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| 290 | * so subsequent calls are fast.  | 
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| 291 | *  | 
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| 292 | * @param string $tableName Table name column resides in  | 
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| 293 | * @param string $columnName Column name the constraint is for  | 
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| 294 | * @return string The check string  | 
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| 295 | */  | 
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| 296 | public function getConstraintCheckClause($tableName, $columnName)  | 
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| 322 | |||
| 323 | /**  | 
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| 324 | * Return the name of the default constraint applied to $tableName.$colName.  | 
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| 325 | * Will return null if no such constraint exists  | 
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| 326 | *  | 
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| 327 | * @param string $tableName Name of the table  | 
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| 328 | * @param string $colName Name of the column  | 
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| 329 | * @return string|null  | 
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| 330 | */  | 
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| 331 | protected function defaultConstraintName($tableName, $colName)  | 
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| 344 | |||
| 345 | /**  | 
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| 346 | * Get enum values from a constraint check clause.  | 
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| 347 | *  | 
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| 348 | * @param string $clause Check clause to parse values from  | 
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| 349 | * @return array Enum values  | 
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| 350 | */  | 
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| 351 | protected function enumValuesFromCheckClause($clause)  | 
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| 363 | |||
| 364 | /*  | 
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| 365 | * Creates an ALTER expression for a column in MS SQL  | 
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| 366 | *  | 
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| 367 | * @param string $tableName Name of the table to be altered  | 
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| 368 | * @param string $colName Name of the column to be altered  | 
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| 369 | * @param string $colSpec String which contains conditions for a column  | 
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| 370 | * @return string  | 
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| 371 | */  | 
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| 372 | protected function alterTableAlterColumn($tableName, $colName, $colSpec)  | 
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| 430 | |||
| 431 | /**  | 
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| 432 | * @param string $oldTableName  | 
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| 433 | * @param string $newTableName  | 
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| 434 | */  | 
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| 435 | public function renameTable($oldTableName, $newTableName)  | 
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| 439 | |||
| 440 | /**  | 
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| 441 | * Checks a table's integrity and repairs it if necessary.  | 
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| 442 | * NOTE: MSSQL does not appear to support any vacuum or optimise commands  | 
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| 443 | *  | 
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| 444 | * @var string $tableName The name of the table.  | 
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| 445 | * @return boolean Return true if the table has integrity after the method is complete.  | 
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| 446 | */  | 
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| 447 | public function checkAndRepairTable($tableName)  | 
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| 451 | |||
| 452 | /**  | 
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| 453 | * @param string $tableName  | 
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| 454 | * @param string $fieldName  | 
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| 455 | * @param string $fieldSpec  | 
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| 456 | */  | 
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| 457 | public function createField($tableName, $fieldName, $fieldSpec)  | 
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| 461 | |||
| 462 | /**  | 
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| 463 | * Change the database type of the given field.  | 
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| 464 | *  | 
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| 465 | * @param string $tableName The name of the tbale the field is in.  | 
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| 466 | * @param string $fieldName The name of the field to change.  | 
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| 467 | * @param string $fieldSpec The new field specification  | 
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| 468 | */  | 
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| 469 | public function alterField($tableName, $fieldName, $fieldSpec)  | 
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| 473 | |||
| 474 | /**  | 
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| 475 | * @param string $tableName  | 
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| 476 | * @param string $oldName  | 
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| 477 | * @param string $newName  | 
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| 478 | *  | 
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| 479 | */  | 
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| 480 | public function renameField($tableName, $oldName, $newName)  | 
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| 484 | |||
| 485 | /**  | 
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| 486 | * @param string $table  | 
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| 487 | *  | 
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| 488 | * @return array  | 
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| 489 | */  | 
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| 490 | public function fieldList($table)  | 
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| 600 | |||
| 601 | /**  | 
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| 602 | * Create an index on a table.  | 
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| 603 | * @param string $tableName The name of the table.  | 
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| 604 | * @param string $indexName The name of the index.  | 
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| 605 | * @param string $indexSpec The specification of the index, see SS_Database::requireIndex() for more details.  | 
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| 606 | */  | 
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| 607 | public function createIndex($tableName, $indexName, $indexSpec)  | 
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| 611 | |||
| 612 | |||
| 613 | /**  | 
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| 614 | * This takes the index spec which has been provided by a class (ie static $indexes = blah blah)  | 
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| 615 | * and turns it into a proper string.  | 
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| 616 | * Some indexes may be arrays, such as fulltext and unique indexes, and this allows database-specific  | 
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| 617 |      * arrays to be created. See {@link requireTable()} for details on the index format. | 
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| 618 | *  | 
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| 619 | * @see http://dev.mysql.com/doc/refman/5.0/en/create-index.html  | 
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| 620 | * @see parseIndexSpec() for approximate inverse  | 
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| 621 | *  | 
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| 622 | * @param string|array $indexSpec  | 
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| 623 | * @return string  | 
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| 624 | */  | 
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| 625 | protected function convertIndexSpec($indexSpec)  | 
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| 632 | |||
| 633 | /**  | 
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| 634 | * Return SQL for dropping and recreating an index  | 
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| 635 | *  | 
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| 636 | * @param string $tableName Name of table to create this index against  | 
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| 637 | * @param string $indexName Name of this index  | 
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| 638 | * @param array|string $indexSpec Index specification, either as a raw string  | 
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| 639 | * or parsed array form  | 
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| 640 | * @return string The SQL required to generate this index  | 
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| 641 | */  | 
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| 642 | protected function getIndexSqlDefinition($tableName, $indexName, $indexSpec)  | 
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| 673 | |||
| 674 | public function alterIndex($tableName, $indexName, $indexSpec)  | 
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| 678 | |||
| 679 | /**  | 
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| 680 | * Return the list of indexes in a table.  | 
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| 681 | *  | 
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| 682 | * @param string $table The table name.  | 
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| 683 | * @return array  | 
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| 684 | */  | 
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| 685 | public function indexList($table)  | 
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| 732 | |||
| 733 | /**  | 
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| 734 | * For a given table name, get all the internal index names,  | 
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| 735 | * except for those that are primary keys and fulltext indexes.  | 
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| 736 | *  | 
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| 737 | * @param string $tableName  | 
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| 738 | * @return array  | 
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| 739 | */  | 
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| 740 | public function indexNames($tableName)  | 
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| 749 | |||
| 750 | public function tableList()  | 
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| 760 | |||
| 761 | /**  | 
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| 762 | * Return a boolean type-formatted string  | 
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| 763 | * We use 'bit' so that we can do numeric-based comparisons  | 
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| 764 | *  | 
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| 765 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 766 | * @return string  | 
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| 767 | */  | 
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| 768 | public function boolean($values)  | 
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| 773 | |||
| 774 | /**  | 
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| 775 | * Return a date type-formatted string.  | 
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| 776 | *  | 
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| 777 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 778 | * @return string  | 
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| 779 | */  | 
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| 780 | public function date($values)  | 
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| 784 | |||
| 785 | /**  | 
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| 786 | * Return a decimal type-formatted string  | 
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| 787 | *  | 
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| 788 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 789 | * @return string  | 
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| 790 | */  | 
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| 791 | public function decimal($values)  | 
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| 808 | |||
| 809 | /**  | 
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| 810 | * Return a enum type-formatted string  | 
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| 811 | *  | 
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| 812 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 813 | * @return string  | 
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| 814 | */  | 
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| 815 | public function enum($values)  | 
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| 827 | |||
| 828 | /**  | 
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| 829 |      * @todo Make this work like {@link MySQLDatabase::set()} | 
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| 830 | *  | 
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| 831 | * @param array $values  | 
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| 832 | * @return string  | 
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| 833 | */  | 
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| 834 | public function set($values)  | 
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| 838 | |||
| 839 | /**  | 
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| 840 | * Return a float type-formatted string.  | 
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| 841 | *  | 
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| 842 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 843 | * @return string  | 
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| 844 | */  | 
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| 845 | public function float($values)  | 
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| 849 | |||
| 850 | /**  | 
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| 851 | * Return a int type-formatted string  | 
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| 852 | *  | 
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| 853 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 854 | * @return string  | 
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| 855 | */  | 
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| 856 | public function int($values)  | 
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| 860 | |||
| 861 | /**  | 
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| 862 | * Return a bigint type-formatted string  | 
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| 863 | *  | 
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| 864 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 865 | * @return string  | 
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| 866 | */  | 
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| 867 | public function bigint($values)  | 
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| 871 | |||
| 872 | /**  | 
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| 873 | * Return a datetime type-formatted string  | 
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| 874 | * For MS SQL, we simply return the word 'timestamp', no other parameters are necessary  | 
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| 875 | *  | 
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| 876 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 877 | * @return string  | 
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| 878 | */  | 
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| 879 | public function datetime($values)  | 
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| 883 | |||
| 884 | /**  | 
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| 885 | * Return a text type-formatted string  | 
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| 886 | *  | 
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| 887 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 888 | * @return string  | 
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| 889 | */  | 
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| 890 | public function text($values)  | 
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| 896 | |||
| 897 | /**  | 
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| 898 | * Return a time type-formatted string.  | 
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| 899 | *  | 
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| 900 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 901 | * @return string  | 
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| 902 | */  | 
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| 903 | public function time($values)  | 
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| 907 | |||
| 908 | /**  | 
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| 909 | * Return a varchar type-formatted string  | 
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| 910 | *  | 
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| 911 | * @param array $values Contains a tokenised list of info about this data type  | 
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| 912 | * @return string  | 
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| 913 | */  | 
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| 914 | public function varchar($values)  | 
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| 920 | |||
| 921 | /**  | 
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| 922 | * Return a 4 digit numeric type.  | 
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| 923 | *  | 
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| 924 | * @param array $values  | 
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| 925 | * @return string  | 
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| 926 | */  | 
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| 927 | public function year($values)  | 
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| 931 | |||
| 932 | /**  | 
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| 933 | * This returns the column which is the primary key for each table  | 
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| 934 | *  | 
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| 935 | * @param bool $asDbValue  | 
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| 936 | * @param bool $hasAutoIncPK  | 
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| 937 | * @return string  | 
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| 938 | */  | 
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| 939 | public function IdColumn($asDbValue = false, $hasAutoIncPK = true)  | 
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| 949 | |||
| 950 | public function hasTable($tableName)  | 
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| 957 | |||
| 958 | /**  | 
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| 959 | * Returns the values of the given enum field  | 
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| 960 | * NOTE: Experimental; introduced for db-abstraction and may changed before 2.4 is released.  | 
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| 961 | *  | 
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| 962 | * @param string $tableName  | 
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| 963 | * @param string $fieldName  | 
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| 964 | * @return array  | 
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| 965 | */  | 
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| 966 | public function enumValuesForField($tableName, $fieldName)  | 
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| 978 | |||
| 979 | /**  | 
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| 980 | * @param string $type  | 
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| 981 | * @return string  | 
            ||
| 982 | */  | 
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| 983 | public function dbDataType($type)  | 
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| 995 | |||
| 996 | /**  | 
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| 997 | * @param string $tableName  | 
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| 998 | * @param string $indexName  | 
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| 999 | * @param mixed $spec  | 
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| 1000 | */  | 
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| 1001 | protected function indexKey($tableName, $indexName, $spec)  | 
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| 1005 | }  | 
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| 1006 | 
Let’s take a look at an example:
In the above example, the authenticate() method works fine as long as you just pass instances of MyUser. However, if you now also want to pass a different sub-classes of User which does not have a getDisplayName() method, the code will break.
Available Fixes
Change the type-hint for the parameter:
Add an additional type-check:
Add the method to the parent class: