Merge "Database: Fix degenerate parenthesized joins"

diff --combined includes/libs/rdbms/database/Database.php
index 5edf3fd,b936779..e10746c
--- 1/includes/libs/rdbms/database/Database.php
--- 2/includes/libs/rdbms/database/Database.php
+++ b/includes/libs/rdbms/database/Database.php
@@@ -461,12 -461,9 +461,12 @@@ abstract class Database implements IDat
        protected function ignoreErrors( $ignoreErrors = null ) {
                $res = $this->getFlag( self::DBO_IGNORE );
                if ( $ignoreErrors !== null ) {
 -                      $ignoreErrors
 -                              ? $this->setFlag( self::DBO_IGNORE )
 -                              : $this->clearFlag( self::DBO_IGNORE );
 +                      // setFlag()/clearFlag() do not allow DBO_IGNORE changes for sanity
 +                      if ( $ignoreErrors ) {
 +                              $this->mFlags |= self::DBO_IGNORE;
 +                      } else {
 +                              $this->mFlags &= ~self::DBO_IGNORE;
 +                      }
                }
  
                return $res;
@@@ -624,10 -621,6 +624,10 @@@
        }
  
        public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 +              if ( ( $flag & self::DBO_IGNORE ) ) {
 +                      throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 +              }
 +
                if ( $remember === self::REMEMBER_PRIOR ) {
                        array_push( $this->priorFlags, $this->mFlags );
                }
@@@ -635,10 -628,6 +635,10 @@@
        }
  
        public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 +              if ( ( $flag & self::DBO_IGNORE ) ) {
 +                      throw new \UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 +              }
 +
                if ( $remember === self::REMEMBER_PRIOR ) {
                        array_push( $this->priorFlags, $this->mFlags );
                }
@@@ -2030,9 -2019,19 +2030,19 @@@
  
                        if ( is_array( $table ) ) {
                                // A parenthesized group
-                               $joinedTable = '('
-                                       . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
-                                       . ')';
+                               if ( count( $table ) > 1 ) {
+                                       $joinedTable = '('
+                                               . $this->tableNamesWithIndexClauseOrJOIN( $table, $use_index, $ignore_index, $join_conds )
+                                               . ')';
+                               } else {
+                                       // Degenerate case
+                                       $innerTable = reset( $table );
+                                       $innerAlias = key( $table );
+                                       $joinedTable = $this->tableNameWithAlias(
+                                               $innerTable,
+                                               is_string( $innerAlias ) ? $innerAlias : $innerTable
+                                       );
+                               }
                        } else {
                                $joinedTable = $this->tableNameWithAlias( $table, $alias );
                        }