Avoid checking double-prefixed table names in mysql tableExists()

Change-Id: I9d91a5305227171d0776ffa443d4e538fbe1b15f

diff --git a/includes/libs/rdbms/database/Database.php b/includes/libs/rdbms/database/Database.php
index afeffb3..559c28b 100644 (file)
--- a/includes/libs/rdbms/database/Database.php
+++ b/includes/libs/rdbms/database/Database.php
@@ -1822,8 +1822,10 @@ abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAware
        }
 
        /**
-        * @param string $name Table name
-        * @return array (DB name, schema name, table prefix, table name)
+        * Get the table components needed for a query given the currently selected database
+        *
+        * @param string $name Table name in the form of db.schema.table, db.table, or table
+        * @return array (DB name or "" for default, schema name, table prefix, table name)
         */
        protected function qualifiedTableComponents( $name ) {
                # We reverse the explode so that database.table and table both output the correct table.

diff --git a/includes/libs/rdbms/database/DatabaseMysqlBase.php b/includes/libs/rdbms/database/DatabaseMysqlBase.php
index e237ef4..8d19bc1 100644 (file)
--- a/includes/libs/rdbms/database/DatabaseMysqlBase.php
+++ b/includes/libs/rdbms/database/DatabaseMysqlBase.php
@@ -527,25 +527,23 @@ abstract class DatabaseMysqlBase extends Database {
        }
 
        public function tableExists( $table, $fname = __METHOD__ ) {
-               $table = $this->tableName( $table, 'raw' );
-               if ( isset( $this->mSessionTempTables[$table] ) ) {
-                       return true; // already known to exist and won't show in SHOW TABLES anyway
-               }
-
                // Split database and table into proper variables as Database::tableName() returns
                // shared tables prefixed with their database, which do not work in SHOW TABLES statements
-               list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $table );
+               list( $database, , $prefix, $table ) = $this->qualifiedTableComponents( $table );
+               $tableName = "{$prefix}{$table}";
 
-               $table = $prefix . $table;
+               if ( isset( $this->mSessionTempTables[$tableName] ) ) {
+                       return true; // already known to exist and won't show in SHOW TABLES anyway
+               }
 
                // We can't use buildLike() here, because it specifies an escape character
                // other than the backslash, which is the only one supported by SHOW TABLES
-               $encLike = $this->escapeLikeInternal( $table, '\\' );
+               $encLike = $this->escapeLikeInternal( $tableName, '\\' );
 
-               // If the database has been specified (such as for shared tables), add a FROM $database clause
+               // If the database has been specified (such as for shared tables), use "FROM"
                if ( $database !== '' ) {
-                       $database = $this->addIdentifierQuotes( $database );
-                       $query = "SHOW TABLES FROM $database LIKE '$encLike'";
+                       $encDatabase = $this->addIdentifierQuotes( $database );
+                       $query = "SHOW TABLES FROM $encDatabase LIKE '$encLike'";
                } else {
                        $query = "SHOW TABLES LIKE '$encLike'";
                }