Complex classes like Schema 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 Schema, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 33 | class Schema extends \yii\db\Schema implements ConstraintFinderInterface  | 
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| 34 | { | 
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| 35 | use ConstraintFinderTrait;  | 
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| 36 | |||
| 37 | /**  | 
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| 38 | * @var array mapping from physical column types (keys) to abstract column types (values)  | 
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| 39 | */  | 
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| 40 | public $typeMap = [  | 
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| 41 | 'tinyint' => self::TYPE_SMALLINT,  | 
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| 42 | 'bit' => self::TYPE_SMALLINT,  | 
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| 43 | 'boolean' => self::TYPE_BOOLEAN,  | 
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| 44 | 'bool' => self::TYPE_BOOLEAN,  | 
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| 45 | 'smallint' => self::TYPE_SMALLINT,  | 
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| 46 | 'mediumint' => self::TYPE_INTEGER,  | 
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| 47 | 'int' => self::TYPE_INTEGER,  | 
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| 48 | 'integer' => self::TYPE_INTEGER,  | 
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| 49 | 'bigint' => self::TYPE_BIGINT,  | 
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| 50 | 'float' => self::TYPE_FLOAT,  | 
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| 51 | 'double' => self::TYPE_DOUBLE,  | 
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| 52 | 'real' => self::TYPE_FLOAT,  | 
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| 53 | 'decimal' => self::TYPE_DECIMAL,  | 
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| 54 | 'numeric' => self::TYPE_DECIMAL,  | 
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| 55 | 'tinytext' => self::TYPE_TEXT,  | 
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| 56 | 'mediumtext' => self::TYPE_TEXT,  | 
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| 57 | 'longtext' => self::TYPE_TEXT,  | 
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| 58 | 'text' => self::TYPE_TEXT,  | 
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| 59 | 'varchar' => self::TYPE_STRING,  | 
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| 60 | 'string' => self::TYPE_STRING,  | 
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| 61 | 'char' => self::TYPE_CHAR,  | 
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| 62 | 'blob' => self::TYPE_BINARY,  | 
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| 63 | 'datetime' => self::TYPE_DATETIME,  | 
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| 64 | 'year' => self::TYPE_DATE,  | 
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| 65 | 'date' => self::TYPE_DATE,  | 
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| 66 | 'time' => self::TYPE_TIME,  | 
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| 67 | 'timestamp' => self::TYPE_TIMESTAMP,  | 
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| 68 | 'enum' => self::TYPE_STRING,  | 
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| 69 | ];  | 
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| 70 | |||
| 71 | /**  | 
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| 72 | * @inheritDoc  | 
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| 73 | */  | 
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| 74 | protected $tableQuoteCharacter = '`';  | 
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| 75 | /**  | 
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| 76 | * @inheritDoc  | 
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| 77 | */  | 
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| 78 | protected $columnQuoteCharacter = '`';  | 
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| 79 | |||
| 80 | |||
| 81 | /**  | 
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| 82 | * @inheritDoc  | 
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| 83 | */  | 
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| 84 | 6 | protected function findTableNames($schema = '')  | 
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| 89 | |||
| 90 | /**  | 
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| 91 | * @inheritDoc  | 
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| 92 | */  | 
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| 93 | 266 | protected function loadTableSchema($name)  | 
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| 106 | |||
| 107 | /**  | 
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| 108 | * @inheritDoc  | 
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| 109 | */  | 
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| 110 | 34 | protected function loadTablePrimaryKey($tableName)  | 
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| 114 | |||
| 115 | /**  | 
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| 116 | * @inheritDoc  | 
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| 117 | */  | 
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| 118 | 3 | protected function loadTableForeignKeys($tableName)  | 
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| 137 | |||
| 138 | /**  | 
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| 139 | * @inheritDoc  | 
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| 140 | */  | 
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| 141 | 10 | protected function loadTableIndexes($tableName)  | 
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| 145 | |||
| 146 | /**  | 
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| 147 | * @inheritDoc  | 
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| 148 | */  | 
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| 149 | 12 | protected function loadTableUniques($tableName)  | 
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| 153 | |||
| 154 | /**  | 
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| 155 | * @inheritDoc  | 
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| 156 | */  | 
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| 157 | 12 | protected function loadTableChecks($tableName)  | 
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| 192 | |||
| 193 | /**  | 
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| 194 | * @inheritDoc  | 
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| 195 | * @throws NotSupportedException if this method is called.  | 
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| 196 | */  | 
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| 197 | 12 | protected function loadTableDefaultValues($tableName)  | 
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| 201 | |||
| 202 | /**  | 
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| 203 | * Creates a query builder for the MySQL database.  | 
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| 204 | * This method may be overridden by child classes to create a DBMS-specific query builder.  | 
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| 205 | * @return QueryBuilder query builder instance  | 
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| 206 | */  | 
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| 207 | 248 | public function createQueryBuilder()  | 
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| 211 | |||
| 212 | /**  | 
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| 213 |      * {@inheritdoc} | 
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| 214 | * @return ColumnSchemaBuilder column schema builder instance  | 
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| 215 | */  | 
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| 216 | 10 | public function createColumnSchemaBuilder($type, $length = null)  | 
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| 220 | |||
| 221 | /**  | 
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| 222 | * Collects the table column metadata.  | 
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| 223 | * @param TableSchema $table the table metadata  | 
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| 224 | * @return bool whether the table exists in the database  | 
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| 225 | */  | 
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| 226 | 266 | protected function findColumns($table)  | 
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| 248 | |||
| 249 | /**  | 
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| 250 | * Collects the foreign key column details for the given table.  | 
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| 251 | * @param TableSchema $table the table metadata  | 
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| 252 | */  | 
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| 253 | 244 | protected function findConstraints($table)  | 
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| 267 | |||
| 268 | /**  | 
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| 269 | * Returns all unique indexes for the given table.  | 
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| 270 | *  | 
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| 271 | * Each array element is of the following structure:  | 
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| 272 | *  | 
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| 273 | * ```php  | 
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| 274 | * [  | 
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| 275 | * 'IndexName1' => ['col1' [, ...]],  | 
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| 276 | * 'IndexName2' => ['col2' [, ...]],  | 
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| 277 | * ]  | 
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| 278 | * ```  | 
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| 279 | *  | 
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| 280 | * @param TableSchema $table the table metadata  | 
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| 281 | * @return array all unique indexes for the given table.  | 
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| 282 | */  | 
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| 283 | 1 | public function findUniqueIndexes($table)  | 
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| 303 | |||
| 304 | /**  | 
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| 305 | * Loads the column information into a [[ColumnSchema]] object.  | 
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| 306 | * @param array $info column information  | 
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| 307 | * @return ColumnSchema the column schema object  | 
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| 308 | */  | 
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| 309 | 244 | protected function loadColumnSchema($info)  | 
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| 358 | |||
| 359 | /**  | 
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| 360 | * Sets the isolation level of the current transaction.  | 
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| 361 | * @param string $level The transaction isolation level to use for this transaction.  | 
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| 362 | * This can be either [[Transaction::READ_UNCOMMITTED]] or [[Transaction::SERIALIZABLE]].  | 
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| 363 | * @throws NotSupportedException when unsupported isolation levels are used.  | 
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| 364 | * SQLite only supports SERIALIZABLE and READ UNCOMMITTED.  | 
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| 365 | * @see http://www.sqlite.org/pragma.html#pragma_read_uncommitted  | 
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| 366 | */  | 
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| 367 | 2 | public function setTransactionIsolationLevel($level)  | 
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| 380 | |||
| 381 | /**  | 
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| 382 | * Loads multiple types of constraints and returns the specified ones.  | 
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| 383 | * @param string $tableName table name.  | 
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| 384 | * @param string $returnType return type:  | 
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| 385 | * - primaryKey  | 
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| 386 | * - indexes  | 
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| 387 | * - uniques  | 
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| 388 | * @return mixed constraints.  | 
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| 389 | */  | 
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| 390 | 56 | private function loadTableConstraints($tableName, $returnType)  | 
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| 445 | |||
| 446 | /**  | 
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| 447 | * Return whether the specified identifier is a SQLite system identifier.  | 
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| 448 | * @param string $identifier  | 
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| 449 | * @return bool  | 
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| 450 | * @see https://www.sqlite.org/src/artifact/74108007d286232f  | 
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| 451 | */  | 
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| 452 | private function isSystemIdentifier($identifier)  | 
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| 456 | }  | 
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| 457 | 
If a method or function can return multiple different values and unless you are sure that you only can receive a single value in this context, we recommend to add an additional type check:
If this a common case that PHP Analyzer should handle natively, please let us know by opening an issue.