Changeset 30345 for trunk/src/wp-includes/wp-db.php

Timestamp:

11/14/2014 09:27:17 PM (10 years ago)

Author:

pento

Message:

When creating a post containing emoji, the post can be saved incorrectly if MySQL isn't using a character set that supports emoji.

This change prevents the save from occurring, so it can be handled correctly in the UI.

See #21212.

File:

• trunk/src/wp-includes/wp-db.php (modified) (13 diffs)

trunk/src/wp-includes/wp-db.php

@@ -145 +145 @@
 
     /**
+     * Cached column info, for sanity checking data before inserting
+     *
+     * @since 4.1.0
+     * @access protected
+     * @var array
+     */
+    protected $col_meta = array();
+
+    /**
+     * Calculated character sets on tables
+     *
+     * @since 4.1.0
+     * @access protected
+     * @var array
+     */
+    protected $table_charset = array();
+
+    /**
+     * Whether text fields in the current query need to be sanity checked.
+     *
+     * @since 4.1.0
+     * @access protected
+     * @var bool
+     */
+    protected $check_current_query = true;
+
+    /**
      * Saved info on the table column
      *
@@ -648 +675 @@
      */
     public function __set( $name, $value ) {
+        $protected_members = array(
+            'col_meta',
+            'table_charset',
+            'check_current_query',
+        );
+        if (  in_array( $name, $protected_members, true ) ) {
+            return;
+        }
         $this->$name = $value;
     }
@@ -1545 +1580 @@
      */
     public function query( $query ) {
-        if ( ! $this->ready )
+        if ( ! $this->ready ) {
+            $this->check_current_query = true;
             return false;
+        }
 
         /**
@@ -1564 +1601 @@
         // Log how the function was called
         $this->func_call = "\$db->query(\"$query\")";
+
+        // If we're writing to the database, make sure the query will write safely.
+        if ( $this->check_current_query && ! $this->check_ascii( $query ) ) {
+            $stripped_query = $this->strip_invalid_text_from_query( $query );
+            if ( $stripped_query !== $query ) {
+                $this->insert_id = 0;
+                return false;
+            }
+        }
+
+        $this->check_current_query = true;
 
         // Keep track of the last query for debug..
@@ -1738 +1786 @@
      */
     function _insert_replace_helper( $table, $data, $format = null, $type = 'INSERT' ) {
-        if ( ! in_array( strtoupper( $type ), array( 'REPLACE', 'INSERT' ) ) )
+        if ( ! in_array( strtoupper( $type ), array( 'REPLACE', 'INSERT' ) ) ) {
             return false;
+        }
+
+        $data = $this->process_fields( $table, $data, $format );
+        if ( false === $data ) {
+            return false;
+        }
+
+        $formats = $values = array();
+        foreach ( $data as $value ) {
+            $formats[] = $value['format'];
+            $values[]  = $value['value'];
+        }
+
+        $fields  = '`' . implode( '`, `', array_keys( $data ) ) . '`';
+        $formats = implode( ', ', $formats );
+
+        $sql = "$type INTO `$table` ($fields) VALUES ($formats)";
+
         $this->insert_id = 0;
-        $formats = $format = (array) $format;
-        $fields = array_keys( $data );
-        $formatted_fields = array();
-        foreach ( $fields as $field ) {
-            if ( !empty( $format ) )
-                $form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
-            elseif ( isset( $this->field_types[$field] ) )
-                $form = $this->field_types[$field];
-            else
-                $form = '%s';
-            $formatted_fields[] = $form;
-        }
-        $sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES (" . implode( ",", $formatted_fields ) . ")";
-        return $this->query( $this->prepare( $sql, $data ) );
+        $this->check_current_query = false;
+        return $this->query( $this->prepare( $sql, $values ) );
     }
 
@@ -1779 +1833 @@
      */
     public function update( $table, $data, $where, $format = null, $where_format = null ) {
-        if ( ! is_array( $data ) || ! is_array( $where ) )
+        if ( ! is_array( $data ) || ! is_array( $where ) ) {
             return false;
-
-        $formats = $format = (array) $format;
-        $bits = $wheres = array();
-        foreach ( (array) array_keys( $data ) as $field ) {
-            if ( !empty( $format ) )
-                $form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
-            elseif ( isset($this->field_types[$field]) )
-                $form = $this->field_types[$field];
-            else
-                $form = '%s';
-            $bits[] = "`$field` = {$form}";
-        }
-
-        $where_formats = $where_format = (array) $where_format;
-        foreach ( (array) array_keys( $where ) as $field ) {
-            if ( !empty( $where_format ) )
-                $form = ( $form = array_shift( $where_formats ) ) ? $form : $where_format[0];
-            elseif ( isset( $this->field_types[$field] ) )
-                $form = $this->field_types[$field];
-            else
-                $form = '%s';
-            $wheres[] = "`$field` = {$form}";
-        }
-
-        $sql = "UPDATE `$table` SET " . implode( ', ', $bits ) . ' WHERE ' . implode( ' AND ', $wheres );
-        return $this->query( $this->prepare( $sql, array_merge( array_values( $data ), array_values( $where ) ) ) );
+        }
+
+        $data = $this->process_fields( $table, $data, $format );
+        if ( false === $data ) {
+            return false;
+        }
+        $where = $this->process_fields( $table, $where, $where_format );
+        if ( false === $where ) {
+            return false;
+        }
+
+        $fields = $conditions = $values = array();
+        foreach ( $data as $field => $value ) {
+            $fields[] = "`$field` = " . $value['format'];
+            $values[] = $value['value'];
+        }
+        foreach ( $where as $field => $value ) {
+            $conditions[] = "`$field` = " . $value['format'];
+            $values[] = $value['value'];
+        }
+
+        $fields = implode( ', ', $fields );
+        $conditions = implode( ' AND ', $conditions );
+
+        $sql = "UPDATE `$table` SET $fields WHERE $conditions";
+
+        $this->check_current_query = false;
+        return $this->query( $this->prepare( $sql, $values ) );
     }
 
@@ -1828 +1884 @@
      */
     public function delete( $table, $where, $where_format = null ) {
-        if ( ! is_array( $where ) )
+        if ( ! is_array( $where ) ) {
             return false;
-
-        $wheres = array();
-
-        $where_formats = $where_format = (array) $where_format;
-
-        foreach ( array_keys( $where ) as $field ) {
-            if ( !empty( $where_format ) ) {
-                $form = ( $form = array_shift( $where_formats ) ) ? $form : $where_format[0];
+        }
+
+        $where = $this->process_fields( $table, $where, $where_format );
+        if ( false === $where ) {
+            return false;
+        }
+
+        $conditions = $values = array();
+        foreach ( $where as $field => $value ) {
+            $conditions[] = "`$field` = " . $value['format'];
+            $values[] = $value['value'];
+        }
+
+        $conditions = implode( ' AND ', $conditions );
+
+        $sql = "DELETE FROM `$table` WHERE $conditions";
+
+        $this->check_current_query = false;
+        return $this->query( $this->prepare( $sql, $values ) );
+    }
+
+    /**
+     * Processes arrays of field/value pairs and field formats.
+     *
+     * This is a helper method for wpdb's CRUD methods, which take field/value
+     * pairs for inserts, updates, and where clauses. This method first pairs
+     * each value with a format. Then it determines the charset of that field,
+     * using that to determine if any invalid text would be stripped. If text is
+     * stripped, then field processing is rejected and the query fails.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $table  Table name.
+     * @param array  $data   Field/value pair.
+     * @param mixed  $format Format for each field.
+     * @return array|bool Returns an array of fields that contain paired values
+     *                    and formats. Returns false for invalid values.
+     */
+    protected function process_fields( $table, $data, $format ) {
+        $data = $this->process_field_formats( $data, $format );
+        $data = $this->process_field_charsets( $data, $table );
+        if ( false === $data ) {
+            return false;
+        }
+
+        $converted_data = $this->strip_invalid_text( $data );
+
+        if ( $data !== $converted_data ) {
+            return false;
+        }
+
+        return $data;
+    }
+
+    /**
+     * Prepares arrays of value/format pairs as passed to wpdb CRUD methods.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param array $data   Array of fields to values.
+     * @param mixed $format Formats to be mapped to the values in $data.
+     * @return array Array, keyed by field names with values being an array
+     *               of 'value' and 'format' keys.
+     */
+    protected function process_field_formats( $data, $format ) {
+        $formats = $original_formats = (array) $format;
+
+        foreach ( $data as $field => $value ) {
+            $value = array(
+                'value'  => $value,
+                'format' => '%s',
+            );
+
+            if ( ! empty( $format ) ) {
+                $value['format'] = array_shift( $formats );
+                if ( ! $value['format'] ) {
+                    $value['format'] = reset( $original_formats );
+                }
             } elseif ( isset( $this->field_types[ $field ] ) ) {
-                $form = $this->field_types[ $field ];
+                $value['format'] = $this->field_types[ $field ];
+            }
+
+            $data[ $field ] = $value;
+        }
+
+        return $data;
+    }
+
+    /**
+     * Adds field charsets to field/value/format arrays
+     * generated by the process_field_formats() method.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param array  $data  As it comes from the process_field_formats() method.
+     * @param string $table Table name.
+     * @return The same array as $data with additional 'charset' keys.
+     */
+    protected function process_field_charsets( $data, $table ) {
+        foreach ( $data as $field => $value ) {
+            if ( '%d' === $value['format'] || '%f' === $value['format'] ) {
+                // We can skip this field if we know it isn't a string.
+                // This checks %d/%f versus ! %s because it's sprintf() could take more.
+                $value['charset'] = false;
+            } elseif ( $this->check_ascii( $value['value'] ) ) {
+                // If it's ASCII, then we don't need the charset. We can skip this field.
+                $value['charset'] = false;
             } else {
-                $form = '%s';
-            }
-
-            $wheres[] = "$field = $form";
-        }
-
-        $sql = "DELETE FROM $table WHERE " . implode( ' AND ', $wheres );
-        return $this->query( $this->prepare( $sql, $where ) );
-    }
-
+                $value['charset'] = $this->get_col_charset( $table, $field );
+                if ( is_wp_error( $value['charset'] ) ) {
+                    return false;
+                }
+
+                // This isn't ASCII. Don't have strip_invalid_text() re-check.
+                $value['ascii'] = false;
+            }
+
+            $data[ $field ] = $value;
+        }
+
+        return $data;
+    }
 
     /**
@@ -1868 +2028 @@
     public function get_var( $query = null, $x = 0, $y = 0 ) {
         $this->func_call = "\$db->get_var(\"$query\", $x, $y)";
-        if ( $query )
+
+        if ( $query ) {
+            $this->check_current_query = false;
             $this->query( $query );
+        }
 
         // Extract var out of cached results based x,y vals
@@ -1895 +2058 @@
     public function get_row( $query = null, $output = OBJECT, $y = 0 ) {
         $this->func_call = "\$db->get_row(\"$query\",$output,$y)";
-        if ( $query )
+        if ( $query ) {
+            $this->check_current_query = false;
             $this->query( $query );
-        else
+        } else {
             return null;
+        }
 
         if ( !isset( $this->last_result[$y] ) )
@@ -1931 +2096 @@
      */
     public function get_col( $query = null , $x = 0 ) {
-        if ( $query )
+        if ( $query ) {
+            $this->check_current_query = false;
             $this->query( $query );
+        }
 
         $new_array = array();
@@ -1958 +2125 @@
         $this->func_call = "\$db->get_results(\"$query\", $output)";
 
-        if ( $query )
+        if ( $query ) {
+            $this->check_current_query = false;
             $this->query( $query );
-        else
+        } else {
             return null;
+        }
 
         $new_array = array();
@@ -1999 +2168 @@
 
     /**
+     * Retrieves the character set for the given table.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $table Table name.
+     * @return string|WP_Error Table character set, `WP_Error` object if it couldn't be found.
+     */
+    protected function get_table_charset( $table ) {
+        $table = strtolower( $table );
+
+        /**
+         * Filter the table charset value before the DB is checked.
+         *
+         * Passing a non-null value to the filter will effectively short-circuit
+         * checking the DB for the charset, returning that value instead.
+         *
+         * @since 4.1.0
+         *
+         * @param string $charset The character set to use. Default null.
+         * @param string $table   The name of the table being checked.
+         */
+        $charset = apply_filters( 'pre_get_table_charset', null, $table );
+        if ( null !== $charset ) {
+            return $charset;
+        }
+
+        if ( isset( $this->table_charset[ $table ] ) ) {
+            return $this->table_charset[ $table ];
+        }
+
+        $charsets = $columns = array();
+        $results = $this->get_results( "SHOW FULL COLUMNS FROM `$table`" );
+        if ( ! $results ) {
+            return new WP_Error( 'wpdb_get_table_charset_failure' );
+        }
+
+        foreach ( $results as $column ) {
+            $columns[ strtolower( $column->Field ) ] = $column;
+        }
+
+        $this->col_meta[ $table ] = $columns;
+
+        foreach ( $columns as $column ) {
+            if ( $column->Collation ) {
+                list( $charset ) = explode( '_', $column->Collation );
+                $charsets[ strtolower( $charset ) ] = true;
+            }
+
+            list( $type ) = explode( '(', $column->Type );
+
+            // A binary/blob means the whole query gets treated like this.
+            if ( in_array( strtoupper( $type ), array( 'BINARY', 'VARBINARY', 'TINYBLOB', 'MEDIUMBLOB', 'BLOB', 'LONGBLOB' ) ) ) {
+                $this->table_charset[ $table ] = 'binary';
+                return 'binary';
+            }
+        }
+
+        // utf8mb3 is an alias for utf8.
+        if ( isset( $charsets['utf8mb3'] ) ) {
+            $charsets['utf8'] = true;
+            unset( $charsets['utf8mb3'] );
+        }
+
+        // Check if we have more than one charset in play.
+        $count = count( $charsets );
+        if ( 1 === $count ) {
+            $charset = key( $charsets );
+        } elseif ( 0 === $count ) {
+            // No charsets, assume this table can store whatever.
+            $charset = 'latin1';
+        } else {
+            // More than one charset. Remove latin1 if present and recalculate.
+            unset( $charsets['latin1'] );
+            $count = count( $charsets );
+            if ( 1 === $count ) {
+                // Only one charset (besides latin1).
+                $charset = key( $charsets );
+            } elseif ( 2 === $count && isset( $charsets['utf8'], $charsets['utf8mb4'] ) ) {
+                // Two charsets, but they're utf8 and utf8mb4, use utf8.
+                $charset = 'utf8';
+            } else {
+                // Two mixed character sets. ascii.
+                $charset = 'ascii';
+            }
+        }
+
+        $this->table_charset[ $table ] = $charset;
+        return $charset;
+    }
+
+    /**
+     * Retrieves the character set for the given column.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $table  Table name.
+     * @param string $column Column name.
+     * @return mixed Column character set as a string.
+     *               False if the column has no character set.
+     *               `WP_Error` object if there was an error.
+     */
+    protected function get_col_charset( $table, $column ) {
+        $table = strtolower( $table );
+        $column = strtolower( $column );
+
+        /**
+         * Filter the column charset value before the DB is checked.
+         *
+         * Passing a non-null value to the filter will short-circuit
+         * checking the DB for the charset, returning that value instead.
+         *
+         * @since 4.1.0
+         *
+         * @param string $charset The character set to use. Default null.
+         * @param string $table   The name of the table being checked.
+         * @param string $column  The name of the column being checked.
+         */
+        $charset = apply_filters( 'pre_get_col_charset', null, $table, $column );
+        if ( null !== $charset ) {
+            return $charset;
+        }
+
+        if ( empty( $this->table_charset[ $table ] ) ) {
+            // This primes column information for us.
+            $table_charset = $this->get_table_charset( $table );
+            if ( is_wp_error( $table_charset ) ) {
+                return $table_charset;
+            }
+        }
+
+        // If still no column information, return the table charset.
+        if ( empty( $this->col_meta[ $table ] ) ) {
+            return $this->table_charset[ $table ];
+        }
+
+        // If this column doesn't exist, return the table charset.
+        if ( empty( $this->col_meta[ $table ][ $column ] ) ) {
+            return $this->table_charset[ $table ];
+        }
+
+        // Return false when it's not a string column.
+        if ( empty( $this->col_meta[ $table ][ $column ]->Collation ) ) {
+            return false;
+        }
+
+        list( $charset ) = explode( '_', $this->col_meta[ $table ][ $column ]->Collation );
+        return $charset;
+    }
+
+    /**
+     * Check if a string is ASCII.
+     *
+     * The negative regex is faster for non-ASCII strings, as it allows
+     * the search to finish as soon as it encounters a non-ASCII character.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $string String to check.
+     * @return bool True if ASCII, false if not.
+     */
+    protected function check_ascii( $string ) {
+        if ( function_exists( 'mb_check_encoding' ) ) {
+            if ( mb_check_encoding( $string, 'ASCII' ) ) {
+                return true;
+            }
+        } elseif ( ! preg_match( '/[^\x00-\x7F]/', $string ) ) {
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * Strips any invalid characters based on value/charset pairs.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param array $data Array of value arrays. Each value array has the keys
+     *                    'value' and 'charset'. An optional 'ascii' key can be
+     *                    set to false to avoid redundant ASCII checks.
+     * @return array|WP_Error The $data parameter, with invalid characters removed from
+     *                        each value. This works as a passthrough: any additional keys
+     *                        such as 'field' are retained in each value array. If we cannot
+     *                        remove invalid characters, a `WP_Error` object is returned.
+     */
+    protected function strip_invalid_text( $data ) {
+        // Some multibyte character sets that we can check in PHP.
+        $mb_charsets = array(
+            'ascii'   => 'ASCII',
+            'big5'    => 'BIG-5',
+            'eucjpms' => 'eucJP-win',
+            'gb2312'  => 'EUC-CN',
+            'ujis'    => 'EUC-JP',
+            'utf32'   => 'UTF-32',
+            'utf8mb4' => 'UTF-8',
+        );
+
+        $supported_charsets = array();
+        if ( function_exists( 'mb_list_encodings' ) ) {
+            $supported_charsets = mb_list_encodings();
+        }
+
+        $db_check_string = false;
+
+        foreach ( $data as &$value ) {
+            $charset = $value['charset'];
+
+            // latin1 will happily store anything.
+            if ( 'latin1' === $charset ) {
+                continue;
+            }
+
+            // Column or value isn't a string.
+            if ( false === $charset || ! is_string( $value['value'] ) ) {
+                continue;
+            }
+
+            // ASCII is always OK.
+            if ( ! isset( $value['ascii'] ) && $this->check_ascii( $value['value'] ) ) {
+                continue;
+            }
+
+            // Convert the text locally.
+            if ( $supported_charsets ) {
+                if ( isset( $mb_charsets[ $charset ] ) && in_array( $mb_charsets[ $charset ], $supported_charsets ) ) {
+                    $value['value'] = mb_convert_encoding( $value['value'], $mb_charsets[ $charset ], $mb_charsets[ $charset ] );
+                    continue;
+                }
+            }
+
+            // utf8(mb3) can be handled by regex, which is a bunch faster than a DB lookup.
+            if ( 'utf8' === $charset || 'utf8mb3' === $charset ) {
+                $regex = '/
+                    (
+                        (?: [\x00-\x7F]                  # single-byte sequences   0xxxxxxx
+                        |   [\xC2-\xDF][\x80-\xBF]       # double-byte sequences   110xxxxx 10xxxxxx
+                        |   \xE0[\xA0-\xBF][\x80-\xBF]   # triple-byte sequences   1110xxxx 10xxxxxx * 2
+                        |   [\xE1-\xEC][\x80-\xBF]{2}
+                        |   \xED[\x80-\x9F][\x80-\xBF]
+                        |   [\xEE-\xEF][\x80-\xBF]{2}
+                        ){1,100}                         # ...one or more times
+                    )
+                    | .                                  # anything else
+                    /x';
+                $value['value'] = preg_replace( $regex, '$1', $value['value'] );
+                continue;
+            }
+
+            // We couldn't use any local conversions, send it to the DB.
+            $value['db'] = $db_check_string = true;
+        }
+        unset( $value ); // Remove by reference.
+
+        if ( $db_check_string ) {
+            $queries = array();
+            foreach ( $data as $col => $value ) {
+                if ( ! empty( $value['db'] ) ) {
+                    if ( ! isset( $queries[ $value['charset'] ] ) ) {
+                        $queries[ $value['charset'] ] = array();
+                    }
+
+                    // Split the CONVERT() calls by charset, so we can make sure the connection is right
+                    $queries[ $value['charset'] ][ $col ] = $this->prepare( "CONVERT( %s USING {$value['charset']} )", $value['value'] );
+                }
+            }
+
+            $connection_charset = $this->charset;
+            foreach ( $queries as $charset => $query ) {
+                if ( ! $query ) {
+                    continue;
+                }
+
+                // Change the charset to match the string(s) we're converting
+                if ( $charset !== $this->charset ) {
+                    $this->set_charset( $this->dbh, $charset );
+                }
+
+                $row = $this->get_row( "SELECT " . implode( ', ', $query ), ARRAY_N );
+                if ( ! $row ) {
+                    $this->set_charset( $this->dbh, $connection_charset );
+                    return new WP_Error( 'wpdb_strip_invalid_text_failure' );
+                }
+
+                $cols = array_keys( $query );
+                $col_count = count( $cols );
+                for ( $ii = 0; $ii < $col_count; $ii++ ) {
+                    $data[ $cols[ $ii ] ]['value'] = $row[ $ii ];
+                }
+            }
+
+            // Don't forget to change the charset back!
+            if ( $connection_charset !== $this->charset ) {
+                $this->set_charset( $this->dbh, $connection_charset );
+            }
+        }
+
+        return $data;
+    }
+
+    /**
+     * Strips any invalid characters from the query.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $query Query to convert.
+     * @return string|WP_Error The converted query, or a `WP_Error` object if the conversion fails.
+     */
+    protected function strip_invalid_text_from_query( $query ) {
+        $table = $this->get_table_from_query( $query );
+        if ( $table ) {
+            $charset = $this->get_table_charset( $table );
+            if ( is_wp_error( $charset ) ) {
+                return $charset;
+            }
+
+            // We can't reliably strip text from tables containing binary/blob columns
+            if ( 'binary' === $charset ) {
+                return $query;
+            }
+        } else {
+            $charset = $this->charset;
+        }
+
+        $data = array(
+            'value'   => $query,
+            'charset' => $charset,
+            'ascii'   => false,
+        );
+
+        $data = $this->strip_invalid_text( array( $data ) );
+        if ( is_wp_error( $data ) ) {
+            return $data;
+        }
+
+        return $data[0]['value'];
+    }
+
+    /**
+     * Strips any invalid characters from the string for a given table and column.
+     *
+     * @since 4.1.0
+     * @access public
+     *
+     * @param string $table  Table name.
+     * @param string $column Column name.
+     * @param string $value  The text to check.
+     * @return string|WP_Error The converted string, or a `WP_Error` object if the conversion fails.
+     */
+    public function strip_invalid_text_for_column( $table, $column, $value ) {
+        if ( $this->check_ascii( $value ) || ! is_string( $value ) ) {
+            return $value;
+        }
+
+        $charset = $this->get_col_charset( $table, $column );
+        if ( ! $charset ) {
+            // Not a string column.
+            return $value;
+        } elseif ( is_wp_error( $charset ) ) {
+            // Bail on real errors.
+            return $charset;
+        }
+
+        $data = array(
+            $column => array(
+                'value'   => $value,
+                'charset' => $charset,
+                'ascii'   => false,
+            )
+        );
+
+        $data = $this->strip_invalid_text( $data );
+        if ( is_wp_error( $data ) ) {
+            return $data;
+        }
+
+        return $data[ $column ]['value'];
+    }
+
+    /**
+     * Find the first table name referenced in a query.
+     *
+     * @since 4.1.0
+     * @access protected
+     *
+     * @param string $query The query to search.
+     * @return string|bool $table The table name found, or false if a table couldn't be found.
+     */
+    protected function get_table_from_query( $query ) {
+        // Remove characters that can legally trail the table name.
+        $query = rtrim( $query, ';/-#' );
+
+        // Allow (select...) union [...] style queries. Use the first query's table name.
+        $query = ltrim( $query, "\r\n\t (" );
+
+        /*
+         * Strip everything between parentheses except nested selects and use only 1,000
+         * chars of the query.
+         */
+        $query = preg_replace( '/\((?!\s*select)[^(]*?\)/is', '()', substr( $query, 0, 1000 ) );
+
+        // Quickly match most common queries.
+        if ( preg_match( '/^\s*(?:'
+                . 'SELECT.*?\s+FROM'
+                . '|INSERT(?:\s+LOW_PRIORITY|\s+DELAYED|\s+HIGH_PRIORITY)?(?:\s+IGNORE)?(?:\s+INTO)?'
+                . '|REPLACE(?:\s+LOW_PRIORITY|\s+DELAYED)?(?:\s+INTO)?'
+                . '|UPDATE(?:\s+LOW_PRIORITY)?(?:\s+IGNORE)?'
+                . '|DELETE(?:\s+LOW_PRIORITY|\s+QUICK|\s+IGNORE)*(?:\s+FROM)?'
+                . ')\s+`?([\w-]+)`?/is', $query, $maybe ) ) {
+            return $maybe[1];
+        }
+
+        // SHOW TABLE STATUS and SHOW TABLES
+        if ( preg_match( '/^\s*(?:'
+                . 'SHOW\s+TABLE\s+STATUS.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
+                . '|SHOW\s+(?:FULL\s+)?TABLES.+(?:LIKE\s+|WHERE\s+Name\s*=\s*)'
+                . ')\W([\w-]+)\W/is', $query, $maybe ) ) {
+            return $maybe[1];
+        }
+
+        // Big pattern for the rest of the table-related queries.
+        if ( preg_match( '/^\s*(?:'
+                . '(?:EXPLAIN\s+(?:EXTENDED\s+)?)?SELECT.*?\s+FROM'
+                . '|DESCRIBE|DESC|EXPLAIN|HANDLER'
+                . '|(?:LOCK|UNLOCK)\s+TABLE(?:S)?'
+                . '|(?:RENAME|OPTIMIZE|BACKUP|RESTORE|CHECK|CHECKSUM|ANALYZE|REPAIR).*\s+TABLE'
+                . '|TRUNCATE(?:\s+TABLE)?'
+                . '|CREATE(?:\s+TEMPORARY)?\s+TABLE(?:\s+IF\s+NOT\s+EXISTS)?'
+                . '|ALTER(?:\s+IGNORE)?\s+TABLE'
+                . '|DROP\s+TABLE(?:\s+IF\s+EXISTS)?'
+                . '|CREATE(?:\s+\w+)?\s+INDEX.*\s+ON'
+                . '|DROP\s+INDEX.*\s+ON'
+                . '|LOAD\s+DATA.*INFILE.*INTO\s+TABLE'
+                . '|(?:GRANT|REVOKE).*ON\s+TABLE'
+                . '|SHOW\s+(?:.*FROM|.*TABLE)'
+                . ')\s+\(*\s*`?([\w-]+)`?\s*\)*/is', $query, $maybe ) ) {
+            return $maybe[1];
+        }
+
+        return false;
+    }
+
+    /**
      * Load the column metadata from the last query.
      *
@@ -2161 +2777 @@
             case 'set_charset' :
                 return version_compare( $version, '5.0.7', '>=' );
+            case 'utf8mb4' :      // @since 4.1.0
+                return version_compare( $version, '5.5.3', '>=' );
         }