field spec. * @param string $table The table name. * @return array */ abstract protected function fieldList($table); /** * Returns a list of all tables in the database. * Keys are table names in lower case, values are table names in case that * database expects. * @return array */ /** * * This is a stub function. Postgres caches the fieldlist results. * * @param string $tableName * * @return boolean */ public function clearCachedFieldlist($tableName=false){ return true; } abstract protected function tableList(); /** * Returns true if the given table exists in the database */ abstract public function hasTable($tableName); /** * Returns the enum values available on the given field */ abstract public function enumValuesForField($tableName, $fieldName); /** * Returns an escaped string. * * @param string * @return string - escaped string */ abstract public function addslashes($val); /** * The table list, generated by the tableList() function. * Used by the requireTable() function. * @var array */ protected $tableList; /** * The field list, generated by the fieldList() function. * An array of maps of field name => field spec, indexed * by table name. * @var array */ protected $fieldList; /** * The index list for each table, generated by the indexList() function. * An map from table name to an array of index names. * @var array */ protected $indexList; /** * Keeps track whether we are currently updating the schema. */ protected $schemaIsUpdating = false; /** * Large array structure that represents a schema update transaction */ protected $schemaUpdateTransaction; /** * Start a schema-updating transaction. * All calls to requireTable/Field/Index will keep track of the changes requested, but not actually do anything. * Once */ public function beginSchemaUpdate() { $this->schemaIsUpdating = true; $this->tableList = array(); $tables = $this->tableList(); foreach($tables as $table) $this->tableList[strtolower($table)] = $table; $this->indexList = null; $this->fieldList = null; $this->schemaUpdateTransaction = array(); } /** * Completes a schema-updated transaction, executing all the schema chagnes. */ public function endSchemaUpdate() { foreach($this->schemaUpdateTransaction as $tableName => $changes) { switch($changes['command']) { case 'create': $this->createTable($tableName, $changes['newFields'], $changes['newIndexes'], $changes['options'], isset($changes['advancedOptions']) ? $changes['advancedOptions'] : null ); break; case 'alter': $this->alterTable($tableName, $changes['newFields'], $changes['newIndexes'], $changes['alteredFields'], $changes['alteredIndexes'], $changes['alteredOptions'], isset($changes['advancedOptions']) ? $changes['advancedOptions'] : null ); break; } } $this->schemaUpdateTransaction = null; $this->schemaIsUpdating = false; } /** * Cancels the schema updates requested after a beginSchemaUpdate() call. */ public function cancelSchemaUpdate() { $this->schemaUpdateTransaction = null; $this->schemaIsUpdating = false; } /** * Returns true if we are during a schema update. */ function isSchemaUpdating() { return $this->schemaIsUpdating; } /** * Returns true if schema modifications were requested after a beginSchemaUpdate() call. */ public function doesSchemaNeedUpdating() { return (bool)$this->schemaUpdateTransaction; } // Transactional schema altering functions - they don't do anyhting except for update schemaUpdateTransaction /** * @param string $table * @param string $options */ public function transCreateTable($table, $options = null, $advanced_options = null) { $this->schemaUpdateTransaction[$table] = array( 'command' => 'create', 'newFields' => array(), 'newIndexes' => array(), 'options' => $options, 'advancedOptions' => $advanced_options ); } /** * @param string $table * @param array $options */ public function transAlterTable($table, $options, $advanced_options) { $this->transInitTable($table); $this->schemaUpdateTransaction[$table]['alteredOptions'] = $options; $this->schemaUpdateTransaction[$table]['advancedOptions'] = $advanced_options; } public function transCreateField($table, $field, $schema) { $this->transInitTable($table); $this->schemaUpdateTransaction[$table]['newFields'][$field] = $schema; } public function transCreateIndex($table, $index, $schema) { $this->transInitTable($table); $this->schemaUpdateTransaction[$table]['newIndexes'][$index] = $schema; } public function transAlterField($table, $field, $schema) { $this->transInitTable($table); $this->schemaUpdateTransaction[$table]['alteredFields'][$field] = $schema; } public function transAlterIndex($table, $index, $schema) { $this->transInitTable($table); $this->schemaUpdateTransaction[$table]['alteredIndexes'][$index] = $schema; } /** * Handler for the other transXXX methods - mark the given table as being altered * if it doesn't already exist */ protected function transInitTable($table) { if(!isset($this->schemaUpdateTransaction[$table])) { $this->schemaUpdateTransaction[$table] = array( 'command' => 'alter', 'newFields' => array(), 'newIndexes' => array(), 'alteredFields' => array(), 'alteredIndexes' => array(), 'alteredOptions' => '' ); } } /** * Generate the following table in the database, modifying whatever already exists * as necessary. * @todo Change detection for CREATE TABLE $options other than "Engine" * * @param string $table The name of the table * @param string $fieldSchema A list of the fields to create, in the same form as DataObject::$db * @param string $indexSchema A list of indexes to create. See {@link requireIndex()} * @param array $options */ public function requireTable($table, $fieldSchema = null, $indexSchema = null, $hasAutoIncPK=true, $options = Array(), $extensions=false) { if(!isset($this->tableList[strtolower($table)])) { $this->transCreateTable($table, $options, $extensions); $this->alterationMessage("Table $table: created","created"); } else { if(Config::inst()->get('SS_Database', 'check_and_repair_on_build')) { $this->checkAndRepairTable($table, $options); } // Check if options changed $tableOptionsChanged = false; if(isset($options[get_class($this)]) || true) { if(isset($options[get_class($this)])) { if(preg_match('/ENGINE=([^\s]*)/', $options[get_class($this)], $alteredEngineMatches)) { $alteredEngine = $alteredEngineMatches[1]; $tableStatus = DB::query(sprintf( 'SHOW TABLE STATUS LIKE \'%s\'', $table ))->first(); $tableOptionsChanged = ($tableStatus['Engine'] != $alteredEngine); } } } if($tableOptionsChanged || ($extensions && DB::getConn()->supportsExtensions())) $this->transAlterTable($table, $options, $extensions); } //DB ABSTRACTION: we need to convert this to a db-specific version: $this->requireField($table, 'ID', DB::getConn()->IdColumn(false, $hasAutoIncPK)); // Create custom fields if($fieldSchema) { foreach($fieldSchema as $fieldName => $fieldSpec) { //Is this an array field? $arrayValue=''; if(strpos($fieldSpec, '[')!==false){ //If so, remove it and store that info separately $pos=strpos($fieldSpec, '['); $arrayValue=substr($fieldSpec, $pos); $fieldSpec=substr($fieldSpec, 0, $pos); } $fieldObj = Object::create_from_string($fieldSpec, $fieldName); $fieldObj->arrayValue=$arrayValue; $fieldObj->setTable($table); $fieldObj->requireField(); } } // Create custom indexes if($indexSchema) { foreach($indexSchema as $indexName => $indexDetails) { $this->requireIndex($table, $indexName, $indexDetails); } } } /** * If the given table exists, move it out of the way by renaming it to _obsolete_(tablename). * @param string $table The table name. */ public function dontRequireTable($table) { if(isset($this->tableList[strtolower($table)])) { $suffix = ''; while(isset($this->tableList[strtolower("_obsolete_{$table}$suffix")])) { $suffix = $suffix ? ($suffix+1) : 2; } $this->renameTable($table, "_obsolete_{$table}$suffix"); $this->alterationMessage("Table $table: renamed to _obsolete_{$table}$suffix","obsolete"); } } /** * Generate the given index in the database, modifying whatever already exists as necessary. * * The keys of the array are the names of the index. * The values of the array can be one of: * - true: Create a single column index on the field named the same as the index. * - array('type' => 'index|unique|fulltext', 'value' => 'FieldA, FieldB'): This gives you full * control over the index. * * @param string $table The table name. * @param string $index The index name. * @param string|boolean $spec The specification of the index. See requireTable() for more information. */ public function requireIndex($table, $index, $spec) { $newTable = false; //DB Abstraction: remove this ===true option as a possibility? if($spec === true) { $spec = "(\"$index\")"; } //Indexes specified as arrays cannot be checked with this line: (it flattens out the array) if(!is_array($spec)) { $spec = preg_replace('/\s*,\s*/', ',', $spec); } if(!isset($this->tableList[strtolower($table)])) $newTable = true; if(!$newTable && !isset($this->indexList[$table])) { $this->indexList[$table] = $this->indexList($table); } //Fix up the index for database purposes $index=DB::getConn()->getDbSqlDefinition($table, $index, null, true); //Fix the key for database purposes $index_alt=DB::getConn()->modifyIndex($index, $spec); if(!$newTable) { if(isset($this->indexList[$table][$index_alt])) { if(is_array($this->indexList[$table][$index_alt])) { $array_spec = $this->indexList[$table][$index_alt]['spec']; } else { $array_spec = $this->indexList[$table][$index_alt]; } } } if($newTable || !isset($this->indexList[$table][$index_alt])) { $this->transCreateIndex($table, $index, $spec); $this->alterationMessage("Index $table.$index: created as " . DB::getConn()->convertIndexSpec($spec),"created"); } else if($array_spec != DB::getConn()->convertIndexSpec($spec)) { $this->transAlterIndex($table, $index, $spec); $spec_msg=DB::getConn()->convertIndexSpec($spec); $this->alterationMessage("Index $table.$index: changed to $spec_msg" . " (from {$array_spec})","changed"); } } /** * Return true if the table exists and already has a the field specified * @param string $tableName - The table to check * @param string $fieldName - The field to check * @return bool - True if the table exists and the field exists on the table */ public function hasField($tableName, $fieldName) { if (!$this->hasTable($tableName)) return false; $fields = $this->fieldList($tableName); return array_key_exists($fieldName, $fields); } /** * Generate the given field on the table, modifying whatever already exists as necessary. * @param string $table The table name. * @param string $field The field name. * @param array|string $spec The field specification. If passed in array syntax, the specific database * driver takes care of the ALTER TABLE syntax. If passed as a string, its assumed to * be prepared as a direct SQL framgment ready for insertion into ALTER TABLE. In this case you'll * need to take care of database abstraction in your DBField subclass. */ public function requireField($table, $field, $spec) { //TODO: this is starting to get extremely fragmented. //There are two different versions of $spec floating around, and their content changes depending //on how they are structured. This needs to be tidied up. $fieldValue = null; $newTable = false; // backwards compatibility patch for pre 2.4 requireField() calls $spec_orig=$spec; if(!is_string($spec)) { $spec['parts']['name'] = $field; $spec_orig['parts']['name'] = $field; //Convert the $spec array into a database-specific string $spec=DB::getConn()->$spec['type']($spec['parts'], true); } // Collations didn't come in until MySQL 4.1. Anything earlier will throw a syntax error if you try and use // collations. // TODO: move this to the MySQLDatabase file, or drop it altogether? if(!$this->supportsCollations()) { $spec = preg_replace('/ *character set [^ ]+( collate [^ ]+)?( |$)/', '\\2', $spec); } if(!isset($this->tableList[strtolower($table)])) $newTable = true; if(!$newTable && !isset($this->fieldList[$table])) { $this->fieldList[$table] = $this->fieldList($table); } if(is_array($spec)) { $specValue = DB::getConn()->$spec_orig['type']($spec_orig['parts']); } else { $specValue = $spec; } // We need to get db-specific versions of the ID column: if($spec_orig==DB::getConn()->IdColumn() || $spec_orig==DB::getConn()->IdColumn(true)) $specValue=DB::getConn()->IdColumn(true); if(!$newTable) { if(isset($this->fieldList[$table][$field])) { if(is_array($this->fieldList[$table][$field])) { $fieldValue = $this->fieldList[$table][$field]['data_type']; } else { $fieldValue = $this->fieldList[$table][$field]; } } } // Get the version of the field as we would create it. This is used for comparison purposes to see if the // existing field is different to what we now want if(is_array($spec_orig)) { $spec_orig=DB::getConn()->$spec_orig['type']($spec_orig['parts']); } if($newTable || $fieldValue=='') { $this->transCreateField($table, $field, $spec_orig); $this->alterationMessage("Field $table.$field: created as $spec_orig","created"); } else if($fieldValue != $specValue) { // If enums/sets are being modified, then we need to fix existing data in the table. // Update any records where the enum is set to a legacy value to be set to the default. // One hard-coded exception is SiteTree - the default for this is Page. foreach(array('enum','set') as $enumtype) { if(preg_match("/^$enumtype/i",$specValue)) { $newStr = preg_replace("/(^$enumtype\s*\(')|('$\).*)/i","",$spec_orig); $new = preg_split("/'\s*,\s*'/", $newStr); $oldStr = preg_replace("/(^$enumtype\s*\(')|('$\).*)/i","", $fieldValue); $old = preg_split("/'\s*,\s*'/", $newStr); $holder = array(); foreach($old as $check) { if(!in_array($check, $new)) { $holder[] = $check; } } if(count($holder)) { $default = explode('default ', $spec_orig); $default = $default[1]; if($default == "'SiteTree'") $default = "'Page'"; $query = "UPDATE \"$table\" SET $field=$default WHERE $field IN ("; for($i=0;$i+1alterationMessage("Changed $amount rows to default value of field $field" . " (Value: $default)"); } } } $this->transAlterField($table, $field, $spec_orig); $this->alterationMessage( "Field $table.$field: changed to $specValue (from {$fieldValue})", "changed" ); } } /** * If the given field exists, move it out of the way by renaming it to _obsolete_(fieldname). * * @param string $table * @param string $fieldName */ public function dontRequireField($table, $fieldName) { $fieldList = $this->fieldList($table); if(array_key_exists($fieldName, $fieldList)) { $suffix = ''; while(isset($fieldList[strtolower("_obsolete_{$fieldName}$suffix")])) { $suffix = $suffix ? ($suffix+1) : 2; } $this->renameField($table, $fieldName, "_obsolete_{$fieldName}$suffix"); $this->alterationMessage("Field $table.$fieldName: renamed to $table._obsolete_{$fieldName}$suffix", "obsolete"); } } /** * Execute a complex manipulation on the database. * A manipulation is an array of insert / or update sequences. The keys of the array are table names, * and the values are map containing 'command' and 'fields'. Command should be 'insert' or 'update', * and fields should be a map of field names to field values, including quotes. The field value can * also be a SQL function or similar. * @param array $manipulation */ public function manipulate($manipulation) { if($manipulation) foreach($manipulation as $table => $writeInfo) { if(isset($writeInfo['fields']) && $writeInfo['fields']) { $fieldList = $columnList = $valueList = array(); foreach($writeInfo['fields'] as $fieldName => $fieldVal) { $fieldList[] = "\"$fieldName\" = $fieldVal"; $columnList[] = "\"$fieldName\""; // Empty strings inserted as null in INSERTs. Replacement of SS_Database::replace_with_null(). if($fieldVal === "''") $valueList[] = "null"; else $valueList[] = $fieldVal; } if(!isset($writeInfo['where']) && isset($writeInfo['id'])) { $writeInfo['where'] = "\"ID\" = " . (int)$writeInfo['id']; } switch($writeInfo['command']) { case "update": // Test to see if this update query shouldn't, in fact, be an insert if($this->query("SELECT \"ID\" FROM \"$table\" WHERE $writeInfo[where]")->value()) { $fieldList = implode(", ", $fieldList); $sql = "UPDATE \"$table\" SET $fieldList where $writeInfo[where]"; $this->query($sql); break; } // ...if not, we'll skip on to the insert code case "insert": if(!isset($writeInfo['fields']['ID']) && isset($writeInfo['id'])) { $columnList[] = "\"ID\""; $valueList[] = (int)$writeInfo['id']; } $columnList = implode(", ", $columnList); $valueList = implode(", ", $valueList); $sql = "INSERT INTO \"$table\" ($columnList) VALUES ($valueList)"; $this->query($sql); break; default: $sql = null; user_error("SS_Database::manipulate() Can't recognise command '$writeInfo[command]'", E_USER_ERROR); } } } } /** Replaces "\'\'" with "null", recursively walks through the given array. * @param string $array Array where the replacement should happen */ public static function replace_with_null(&$array) { $array = preg_replace('/= *\'\'/', '= null', $array); if(is_array($array)) { foreach($array as $key => $value) { if(is_array($value)) { array_walk($array, array(SS_Database, 'replace_with_null')); } } } return $array; } /** * Error handler for database errors. * All database errors will call this function to report the error. It isn't a static function; * it will be called on the object itself and as such can be overridden in a subclass. * @todo hook this into a more well-structured error handling system. * @param string $msg The error message. * @param int $errorLevel The level of the error to throw. */ public function databaseError($msg, $errorLevel = E_USER_ERROR) { user_error($msg, $errorLevel); } /** * Enable supression of database messages. */ public function quiet() { $this->supressOutput = true; } /** * Show a message about database alteration * * @param string message to display * @param string type one of [created|changed|repaired|obsolete|deleted|error] */ public function alterationMessage($message,$type=""){ if(!$this->supressOutput) { if(Director::is_cli()) { switch ($type){ case "created": case "changed": case "repaired": $sign = "+"; break; case "obsolete": case "deleted": $sign = '-'; break; case "error": $sign = "!"; break; default: $sign=" "; } $message = strip_tags($message); echo " $sign $message\n"; } else { switch ($type){ case "created": $color = "green"; break; case "obsolete": $color = "red"; break; case "error": $color = "red"; break; case "deleted": $color = "red"; break; case "changed": $color = "blue"; break; case "repaired": $color = "blue"; break; default: $color=""; } echo "
  • $message
  • "; } } } /** * Returns the SELECT clauses ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @param array $select Select columns * @param boolean $distinct Distinct select? * @return string */ public function sqlSelectToString($select, $distinct = false) { $clauses = array(); foreach($select as $alias => $field) { // Don't include redundant aliases. if($alias === $field || preg_match('/"' . preg_quote($alias) . '"$/', $field)) $clauses[] = $field; else $clauses[] = "$field AS \"$alias\""; } $text = 'SELECT '; if($distinct) $text .= 'DISTINCT '; return $text .= implode(', ', $clauses); } /** * Return the FROM clause ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlFromToString($from) { return ' FROM ' . implode(' ', $from); } /** * Returns the WHERE clauses ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlWhereToString($where, $connective) { return ' WHERE (' . implode(") {$connective} (" , $where) . ')'; } /** * Returns the ORDER BY clauses ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlOrderByToString($orderby) { $statements = array(); foreach($orderby as $clause => $dir) { $statements[] = trim($clause . ' ' . $dir); } return ' ORDER BY ' . implode(', ', $statements); } /** * Returns the GROUP BY clauses ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlGroupByToString($groupby) { return ' GROUP BY ' . implode(', ', $groupby); } /** * Returns the HAVING clauses ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlHavingToString($having) { return ' HAVING ( ' . implode(' ) AND ( ', $having) . ')'; } /** * Return the LIMIT clause ready for inserting into a query. * Caution: Expects correctly quoted and escaped SQL fragments. * * @return string */ public function sqlLimitToString($limit) { $clause = ''; // Pass limit as array or SQL string value if(is_array($limit)) { if(!array_key_exists('limit', $limit)) { throw new InvalidArgumentException('Database::sqlLimitToString(): Wrong format for $limit: ' . var_export($limit, true)); } if(isset($limit['start']) && is_numeric($limit['start']) && isset($limit['limit']) && is_numeric($limit['limit'])) { $combinedLimit = $limit['start'] ? "$limit[limit] OFFSET $limit[start]" : "$limit[limit]"; } elseif(isset($limit['limit']) && is_numeric($limit['limit'])) { $combinedLimit = (int)$limit['limit']; } else { $combinedLimit = false; } if(!empty($combinedLimit)) $clause .= ' LIMIT ' . $combinedLimit; } else { $clause .= ' LIMIT ' . $limit; } return $clause; } /** * Convert a SQLQuery object into a SQL statement * Caution: Expects correctly quoted and escaped SQL fragments. * * @param $query SQLQuery */ public function sqlQueryToString(SQLQuery $query) { if($query->getDelete()) { $text = 'DELETE '; } else { $text = $this->sqlSelectToString($query->getSelect(), $query->getDistinct()); } if($query->getFrom()) $text .= $this->sqlFromToString($query->getFrom()); if($query->getWhere()) $text .= $this->sqlWhereToString($query->getWhere(), $query->getConnective()); // these clauses only make sense in SELECT queries, not DELETE if(!$query->getDelete()) { if($query->getGroupBy()) $text .= $this->sqlGroupByToString($query->getGroupBy()); if($query->getHaving()) $text .= $this->sqlHavingToString($query->getHaving()); if($query->getOrderBy()) $text .= $this->sqlOrderByToString($query->getOrderBy()); if($query->getLimit()) $text .= $this->sqlLimitToString($query->getLimit()); } return $text; } /** * Wrap a string into DB-specific quotes. MySQL, PostgreSQL and SQLite3 only need single quotes around the string. * MSSQL will overload this and include it's own N prefix to mark the string as unicode, so characters like macrons * are saved correctly. * * @param string $string String to be prepared for database query * @return string Prepared string */ public function prepStringForDB($string) { return "'" . Convert::raw2sql($string) . "'"; } /** * Generate a WHERE clause for text matching. * * @param String $field Quoted field name * @param String $value Escaped search. Can include percentage wildcards. * @param boolean $exact Exact matches or wildcard support. * @param boolean $negate Negate the clause. * @param boolean $caseSensitive Perform case sensitive search. * @return String SQL */ abstract public function comparisonClause($field, $value, $exact = false, $negate = false, $caseSensitive = false); /** * function to return an SQL datetime expression that can be used with the adapter in use * used for querying a datetime in a certain format * @param string $date to be formated, can be either 'now', literal datetime like '1973-10-14 10:30:00' or * field name, e.g. '"SiteTree"."Created"' * @param string $format to be used, supported specifiers: * %Y = Year (four digits) * %m = Month (01..12) * %d = Day (01..31) * %H = Hour (00..23) * %i = Minutes (00..59) * %s = Seconds (00..59) * %U = unix timestamp, can only be used on it's own * @return string SQL datetime expression to query for a formatted datetime */ abstract public function formattedDatetimeClause($date, $format); /** * function to return an SQL datetime expression that can be used with the adapter in use * used for querying a datetime addition * @param string $date, can be either 'now', literal datetime like '1973-10-14 10:30:00' or field name, * e.g. '"SiteTree"."Created"' * @param string $interval to be added, use the format [sign][integer] [qualifier], e.g. -1 Day, +15 minutes, * +1 YEAR * supported qualifiers: * - years * - months * - days * - hours * - minutes * - seconds * This includes the singular forms as well * @return string SQL datetime expression to query for a datetime (YYYY-MM-DD hh:mm:ss) which is the result of * the addition */ abstract public function datetimeIntervalClause($date, $interval); /** * function to return an SQL datetime expression that can be used with the adapter in use * used for querying a datetime substraction * @param string $date1, can be either 'now', literal datetime like '1973-10-14 10:30:00' or field name * e.g. '"SiteTree"."Created"' * @param string $date2 to be substracted of $date1, can be either 'now', literal datetime * like '1973-10-14 10:30:00' or field name, e.g. '"SiteTree"."Created"' * @return string SQL datetime expression to query for the interval between $date1 and $date2 in seconds which * is the result of the substraction */ abstract public function datetimeDifferenceClause($date1, $date2); /** * Can the database override timezone as a connection setting, * or does it use the system timezone exclusively? * * @return Boolean */ abstract public function supportsTimezoneOverride(); /* * Does this database support transactions? * * @return boolean */ abstract public function supportsTransactions(); /* * Start a prepared transaction * See http://developer.postgresql.org/pgdocs/postgres/sql-set-transaction.html for details on * transaction isolation options */ abstract public function transactionStart($transaction_mode=false, $session_characteristics=false); /* * Create a savepoint that you can jump back to if you encounter problems */ abstract public function transactionSavepoint($savepoint); /* * Rollback or revert to a savepoint if your queries encounter problems * If you encounter a problem at any point during a transaction, you may * need to rollback that particular query, or return to a savepoint */ abstract public function transactionRollback($savepoint=false); /* * Commit everything inside this transaction so far */ abstract public function transactionEnd(); /** * Determines if the used database supports application-level locks, * which is different from table- or row-level locking. * See {@link getLock()} for details. * * @return boolean */ public function supportsLocks() { return false; } /** * Returns if the lock is available. * See {@link supportsLocks()} to check if locking is generally supported. * * @return Boolean */ public function canLock($name) { return false; } /** * Sets an application-level lock so that no two processes can run at the same time, * also called a "cooperative advisory lock". * * Return FALSE if acquiring the lock fails; otherwise return TRUE, if lock was acquired successfully. * Lock is automatically released if connection to the database is broken (either normally or abnormally), * making it less prone to deadlocks than session- or file-based locks. * Should be accompanied by a {@link releaseLock()} call after the logic requiring the lock has completed. * Can be called multiple times, in which case locks "stack" (PostgreSQL, SQL Server), * or auto-releases the previous lock (MySQL). * * Note that this might trigger the database to wait for the lock to be released, delaying further execution. * * @param String * @param Int Timeout in seconds * @return Boolean */ public function getLock($name, $timeout = 5) { return false; } /** * Remove an application-level lock file to allow another process to run * (if the execution aborts (e.g. due to an error) all locks are automatically released). * * @param String * @return Boolean */ public function releaseLock($name) { return false; } }