hydrus/hydrus/core/HydrusDB.py

import collections
import distutils.version
import os
import queue
import sqlite3
import traceback
import time

from hydrus.core import HydrusConstants as HC
from hydrus.core import HydrusData
from hydrus.core import HydrusEncryption
from hydrus.core import HydrusExceptions
from hydrus.core import HydrusGlobals as HG
from hydrus.core import HydrusPaths

def CheckCanVacuum( db_path, stop_time = None ):
    
    db = sqlite3.connect( db_path, isolation_level = None, detect_types = sqlite3.PARSE_DECLTYPES )
    
    c = db.cursor()
    
    CheckCanVacuumCursor( db_path, c, stop_time = stop_time )
    
def CheckCanVacuumCursor( db_path, c, stop_time = None ):
    
    ( page_size, ) = c.execute( 'PRAGMA page_size;' ).fetchone()
    ( page_count, ) = c.execute( 'PRAGMA page_count;' ).fetchone()
    ( freelist_count, ) = c.execute( 'PRAGMA freelist_count;' ).fetchone()
    
    db_size = ( page_count - freelist_count ) * page_size
    
    vacuum_estimate = int( db_size * 1.2 )
    
    if stop_time is not None:
        
        approx_vacuum_speed_mb_per_s = 1048576 * 1
        
        approx_vacuum_duration = vacuum_estimate // approx_vacuum_speed_mb_per_s
        
        time_i_will_have_to_start = stop_time - approx_vacuum_duration
        
        if HydrusData.TimeHasPassed( time_i_will_have_to_start ):
            
            raise Exception( 'I believe you need about ' + HydrusData.TimeDeltaToPrettyTimeDelta( approx_vacuum_duration ) + ' to vacuum, but there is not enough time allotted.' )
            
        
    
    ( db_dir, db_filename ) = os.path.split( db_path )
    
    HydrusPaths.CheckHasSpaceForDBTransaction( db_dir, vacuum_estimate )
    
def ReadFromCancellableCursor( cursor, largest_group_size, cancelled_hook = None ):
    
    if cancelled_hook is None:
        
        return cursor.fetchall()
        
    
    NUM_TO_GET = 1
    
    results = []
    
    group_of_results = cursor.fetchmany( NUM_TO_GET )
    
    while len( group_of_results ) > 0:
        
        results.extend( group_of_results )
        
        if cancelled_hook():
            
            break
            
        
        if NUM_TO_GET < largest_group_size:
            
            NUM_TO_GET *= 2
            
        
        group_of_results = cursor.fetchmany( NUM_TO_GET )
        
    
    return results
    
def ReadLargeIdQueryInSeparateChunks( cursor, select_statement, chunk_size ):
    
    table_name = 'tempbigread' + os.urandom( 32 ).hex()
    
    cursor.execute( 'CREATE TEMPORARY TABLE ' + table_name + ' ( job_id INTEGER PRIMARY KEY AUTOINCREMENT, temp_id INTEGER );' )
    
    cursor.execute( 'INSERT INTO ' + table_name + ' ( temp_id ) ' + select_statement ) # given statement should end in semicolon, so we are good
    
    num_to_do = cursor.rowcount
    
    if num_to_do is None or num_to_do == -1:
        
        num_to_do = 0
        
    
    i = 0
    
    while i < num_to_do:
        
        chunk = [ temp_id for ( temp_id, ) in cursor.execute( 'SELECT temp_id FROM ' + table_name + ' WHERE job_id BETWEEN ? AND ?;', ( i, i + chunk_size - 1 ) ) ]
        
        yield chunk
        
        i += chunk_size
        
    
    cursor.execute( 'DROP TABLE ' + table_name + ';' )
    
def VacuumDB( db_path ):
    
    db = sqlite3.connect( db_path, isolation_level = None, detect_types = sqlite3.PARSE_DECLTYPES )
    
    c = db.cursor()
    
    fast_big_transaction_wal = not distutils.version.LooseVersion( sqlite3.sqlite_version ) < distutils.version.LooseVersion( '3.11.0' )
    
    if HG.db_journal_mode == 'WAL' and not fast_big_transaction_wal:
        
        c.execute( 'PRAGMA journal_mode = TRUNCATE;' )
        
    
    if HC.PLATFORM_WINDOWS:
        
        ideal_page_size = 4096
        
    else:
        
        ideal_page_size = 1024
        
    
    ( page_size, ) = c.execute( 'PRAGMA page_size;' ).fetchone()
    
    if page_size != ideal_page_size:
        
        c.execute( 'PRAGMA journal_mode = TRUNCATE;' )
        c.execute( 'PRAGMA page_size = ' + str( ideal_page_size ) + ';' )
        
    
    c.execute( 'PRAGMA auto_vacuum = 0;' ) # none
    
    c.execute( 'VACUUM;' )
    
    c.execute( 'PRAGMA journal_mode = {};'.format( HG.db_journal_mode ) )
    
class HydrusDB( object ):
    
    READ_WRITE_ACTIONS = []
    UPDATE_WAIT = 2
    
    TRANSACTION_COMMIT_TIME = 30
    
    def __init__( self, controller, db_dir, db_name ):
        
        if HydrusPaths.GetFreeSpace( db_dir ) < 500 * 1048576:
            
            raise Exception( 'Sorry, it looks like the db partition has less than 500MB, please free up some space.' )
            
        
        self._controller = controller
        self._db_dir = db_dir
        self._db_name = db_name
        
        TemporaryIntegerTableNameCache()
        
        self._transaction_started = 0
        self._in_transaction = False
        self._transaction_contains_writes = False
        
        self._ssl_cert_filename = '{}.crt'.format( self._db_name )
        self._ssl_key_filename = '{}.key'.format( self._db_name )
        
        self._ssl_cert_path = os.path.join( self._db_dir, self._ssl_cert_filename )
        self._ssl_key_path = os.path.join( self._db_dir, self._ssl_key_filename )
        
        self._last_mem_refresh_time = HydrusData.GetNow()
        self._last_wal_checkpoint_time = HydrusData.GetNow()
        
        main_db_filename = db_name
        
        if not main_db_filename.endswith( '.db' ):
            
            main_db_filename += '.db'
            
        
        self._db_filenames = {}
        
        self._db_filenames[ 'main' ] = main_db_filename
        
        self._durable_temp_db_filename = db_name + '.temp.db'
        
        self._InitExternalDatabases()
        
        self._is_first_start = False
        self._is_db_updated = False
        self._local_shutdown = False
        self._pause_and_disconnect = False
        self._loop_finished = False
        self._ready_to_serve_requests = False
        self._could_not_initialise = False
        
        self._jobs = queue.Queue()
        self._pubsubs = []
        
        self._currently_doing_job = False
        self._current_status = ''
        self._current_job_name = ''
        
        self._db = None
        self._c = None
        
        if os.path.exists( os.path.join( self._db_dir, self._db_filenames[ 'main' ] ) ):
            
            # open and close to clean up in case last session didn't close well
            
            self._InitDB()
            self._CloseDBCursor()
            
        
        self._InitDB()
        
        ( version, ) = self._c.execute( 'SELECT version FROM version;' ).fetchone()
        
        if version > HC.SOFTWARE_VERSION:
            
            self._ReportOverupdatedDB( version )
            
        
        if version < ( HC.SOFTWARE_VERSION - 15 ):
            
            self._ReportUnderupdatedDB( version )
            
        
        if version < HC.SOFTWARE_VERSION - 50:
            
            raise Exception( 'Your current database version of hydrus ' + str( version ) + ' is too old for this software version ' + str( HC.SOFTWARE_VERSION ) + ' to update. Please try updating with version ' + str( version + 45 ) + ' or earlier first.' )
            
        
        self._RepairDB()
        
        while version < HC.SOFTWARE_VERSION:
            
            time.sleep( self.UPDATE_WAIT )
            
            try:
                
                self._BeginImmediate()
                
            except Exception as e:
                
                raise HydrusExceptions.DBAccessException( str( e ) )
                
            
            try:
                
                self._UpdateDB( version )
                
                self._Commit()
                
                self._is_db_updated = True
                
            except:
                
                e = Exception( 'Updating the ' + self._db_name + ' db to version ' + str( version + 1 ) + ' caused this error:' + os.linesep + traceback.format_exc() )
                
                try:
                    
                    self._Rollback()
                    
                except Exception as rollback_e:
                    
                    HydrusData.Print( 'When the update failed, attempting to rollback the database failed.' )
                    
                    HydrusData.PrintException( rollback_e )
                    
                
                raise e
                
            
            ( version, ) = self._c.execute( 'SELECT version FROM version;' ).fetchone()
            
        
        self._CloseDBCursor()
        
        self._controller.CallToThreadLongRunning( self.MainLoop )
        
        while not self._ready_to_serve_requests:
            
            time.sleep( 0.1 )
            
            if self._could_not_initialise:
                
                raise Exception( 'Could not initialise the db! Error written to the log!' )
                
            
        
    
    def _AnalyzeTempTable( self, temp_table_name ):
        
        # this is useful to do after populating a temp table so the query planner can decide which index to use in a big join that uses it
        
        self._c.execute( 'ANALYZE {};'.format( temp_table_name ) )
        self._c.execute( 'ANALYZE mem.sqlite_master;' ) # this reloads the current stats into the query planner, may no longer be needed
        
    
    def _AttachExternalDatabases( self ):
        
        for ( name, filename ) in list(self._db_filenames.items()):
            
            if name == 'main':
                
                continue
                
            
            db_path = os.path.join( self._db_dir, filename )
            
            self._c.execute( 'ATTACH ? AS ' + name + ';', ( db_path, ) )
            
        
        db_path = os.path.join( self._db_dir, self._durable_temp_db_filename )
        
        self._c.execute( 'ATTACH ? AS durable_temp;', ( db_path, ) )
        
    
    def _BeginImmediate( self ):
        
        if not self._in_transaction:
            
            self._c.execute( 'BEGIN IMMEDIATE;' )
            self._c.execute( 'SAVEPOINT hydrus_savepoint;' )
            
            self._transaction_started = HydrusData.GetNow()
            self._in_transaction = True
            
        
    
    def _CleanAfterJobWork( self ):
        
        self._pubsubs = []
        
    
    def _CleanUpCaches( self ):
        
        pass
        
    
    def _CloseDBCursor( self ):
        
        TemporaryIntegerTableNameCache.instance().Clear()
        
        if self._db is not None:
            
            if self._in_transaction:
                
                self._Commit()
                
            
            self._c.close()
            self._db.close()
            
            del self._c
            del self._db
            
            self._db = None
            self._c = None
            
        
    
    def _Commit( self ):
        
        if self._in_transaction:
            
            self._c.execute( 'COMMIT;' )
            
            self._in_transaction = False
            
            if HG.db_journal_mode == 'WAL' and HydrusData.TimeHasPassed( self._last_wal_checkpoint_time + 1800 ):
                
                self._c.execute( 'PRAGMA wal_checkpoint(PASSIVE);' )
                
                self._last_wal_checkpoint_time = HydrusData.GetNow()
                
            
            if HydrusData.TimeHasPassed( self._last_mem_refresh_time + 600 ):
                
                self._c.execute( 'DETACH mem;' )
                self._c.execute( 'ATTACH ":memory:" AS mem;' )
                
                TemporaryIntegerTableNameCache.instance().Clear()
                
                self._last_mem_refresh_time = HydrusData.GetNow()
                
            
        else:
            
            HydrusData.Print( 'Received a call to commit, but was not in a transaction!' )
            
        
    
    def _CreateDB( self ):
        
        raise NotImplementedError()
        
    
    def _CreateIndex( self, table_name, columns, unique = False ):
        
        if '.' in table_name:
            
            table_name_simple = table_name.split( '.' )[1]
            
        else:
            
            table_name_simple = table_name
            
        
        index_name = table_name + '_' + '_'.join( columns ) + '_index'
        
        if unique:
            
            create_phrase = 'CREATE UNIQUE INDEX IF NOT EXISTS '
            
        else:
            
            create_phrase = 'CREATE INDEX IF NOT EXISTS '
            
        
        on_phrase = ' ON ' + table_name_simple + ' (' + ', '.join( columns ) + ');'
        
        statement = create_phrase + index_name + on_phrase
        
        self._c.execute( statement )
        
    
    def _DisplayCatastrophicError( self, text ):
        
        message = 'The db encountered a serious error! This is going to be written to the log as well, but here it is for a screenshot:'
        message += os.linesep * 2
        message += text
        
        HydrusData.DebugPrint( message )
        
    
    def _DoAfterJobWork( self ):
        
        for ( topic, args, kwargs ) in self._pubsubs:
            
            self._controller.pub( topic, *args, **kwargs )
            
        
    
    def _ExecuteManySelectSingleParam( self, query, single_param_iterator ):
        
        select_args_iterator = ( ( param, ) for param in single_param_iterator )
        
        return self._ExecuteManySelect( query, select_args_iterator )
        
    
    def _ExecuteManySelect( self, query, select_args_iterator ):
        
        # back in python 2, we did batches of 256 hash_ids/whatever at a time in big "hash_id IN (?,?,?,?,...)" predicates.
        # this was useful to get over some 100,000 x fetchall() call overhead, but it would sometimes throw the SQLite query planner off and do non-optimal queries
        # (basically, the "hash_id in (256)" would weight the hash_id index request x 256 vs another when comparing the sqlite_stat1 tables, which could lead to WEWLAD for some indices with low median very-high mean skewed distribution
        # python 3 is better about call overhead, so we'll go back to what is pure
        # cursor.executemany SELECT when
        
        for select_args in select_args_iterator:
            
            for result in self._c.execute( query, select_args ):
                
                yield result
                
            
        
    
    def _GenerateDBJob( self, job_type, synchronous, action, *args, **kwargs ):
        
        return HydrusData.JobDatabase( job_type, synchronous, action, *args, **kwargs )
        
    
    def _GetPossibleAdditionalDBFilenames( self ):
        
        return [ self._ssl_cert_filename, self._ssl_key_filename ]
        
    
    def _GetRowCount( self ):
        
        row_count = self._c.rowcount
        
        if row_count == -1: return 0
        else: return row_count
        
    
    def _InitCaches( self ):
        
        pass
        
    
    def _InitDB( self ):
        
        create_db = False
        
        db_path = os.path.join( self._db_dir, self._db_filenames[ 'main' ] )
        
        if not os.path.exists( db_path ):
            
            create_db = True
            
            external_db_paths = [ os.path.join( self._db_dir, self._db_filenames[ db_name ] ) for db_name in self._db_filenames if db_name != 'main' ]
            
            existing_external_db_paths = [ external_db_path for external_db_path in external_db_paths if os.path.exists( external_db_path ) ]
            
            if len( existing_external_db_paths ) > 0:
                
                message = 'Although the external files, "{}" do exist, the main database file, "{}", does not! This makes for an invalid database, and the program will now quit. Please contact hydrus_dev if you do not know how this happened or need help recovering from hard drive failure.'
                
                message = message.format( ', '.join( existing_external_db_paths ), db_path )
                
                raise HydrusExceptions.DBAccessException( message )
                
            
        
        self._InitDBCursor()
        
        result = self._c.execute( 'SELECT 1 FROM sqlite_master WHERE type = ? AND name = ?;', ( 'table', 'version' ) ).fetchone()
        
        if result is None:
            
            create_db = True
            
        
        if create_db:
            
            self._is_first_start = True
            
            self._CreateDB()
            
            self._Commit()
            
            self._BeginImmediate()
            
        
    
    def _InitDBCursor( self ):
        
        self._CloseDBCursor()
        
        db_path = os.path.join( self._db_dir, self._db_filenames[ 'main' ] )
        
        db_just_created = not os.path.exists( db_path )
        
        try:
            
            self._db = sqlite3.connect( db_path, isolation_level = None, detect_types = sqlite3.PARSE_DECLTYPES )
            
            self._last_mem_refresh_time = HydrusData.GetNow()
            
            self._c = self._db.cursor()
            
            if HG.no_db_temp_files:
                
                self._c.execute( 'PRAGMA temp_store = 2;' ) # use memory for temp store exclusively
                
            
            self._AttachExternalDatabases()
            
            self._c.execute( 'ATTACH ":memory:" AS mem;' )
            
        except Exception as e:
            
            raise HydrusExceptions.DBAccessException( 'Could not connect to database! This could be an issue related to WAL and network storage, or something else. If it is not obvious to you, please let hydrus dev know. Error follows:' + os.linesep * 2 + str( e ) )
            
        
        self._last_mem_refresh_time = HydrusData.GetNow()
        
        TemporaryIntegerTableNameCache.instance().Clear()
        
        # durable_temp is not excluded here
        db_names = [ name for ( index, name, path ) in self._c.execute( 'PRAGMA database_list;' ) if name not in ( 'mem', 'temp' ) ]
        
        for db_name in db_names:
            
            # MB -> KB
            cache_size = HG.db_cache_size * 1024
            
            self._c.execute( 'PRAGMA {}.cache_size = -{};'.format( db_name, cache_size ) )
            
            self._c.execute( 'PRAGMA {}.journal_mode = {};'.format( db_name, HG.db_journal_mode ) )
            
            if HG.db_journal_mode in ( 'PERSIST', 'WAL' ):
                
                self._c.execute( 'PRAGMA {}.journal_size_limit = {};'.format( db_name, 1024 ** 3 ) ) # 1GB for now
                
            
            self._c.execute( 'PRAGMA {}.synchronous = {};'.format( db_name, HG.db_synchronous ) )
            
            try:
                
                self._c.execute( 'SELECT * FROM {}.sqlite_master;'.format( db_name ) ).fetchone()
                
            except sqlite3.OperationalError as e:
                
                message = 'The database seemed valid, but hydrus failed to read basic data from it. You may need to run the program in a different journal mode using --db_journal_mode. Full error information:'
                
                message += os.linesep * 2
                message += str( e )
                
                HydrusData.DebugPrint( message )
                
                raise HydrusExceptions.DBAccessException( message )
                
            
        
        try:
            
            self._BeginImmediate()
            
        except Exception as e:
            
            raise HydrusExceptions.DBAccessException( str( e ) )
            
        
    
    def _InitExternalDatabases( self ):
        
        pass
        
    
    def _ManageDBError( self, job, e ):
        
        raise NotImplementedError()
        
    
    def _ProcessJob( self, job ):
        
        job_type = job.GetType()
        
        ( action, args, kwargs ) = job.GetCallableTuple()
        
        try:
            
            if job_type in ( 'read_write', 'write' ):
                
                self._current_status = 'db write locked'
                
                self._transaction_contains_writes = True
                
            else:
                
                self._current_status = 'db read locked'
                
            
            self.publish_status_update()
            
            if job_type in ( 'read', 'read_write' ):
                
                result = self._Read( action, *args, **kwargs )
                
            elif job_type in ( 'write' ):
                
                result = self._Write( action, *args, **kwargs )
                
            
            if self._transaction_contains_writes and HydrusData.TimeHasPassed( self._transaction_started + self.TRANSACTION_COMMIT_TIME ):
                
                self._current_status = 'db committing'
                
                self.publish_status_update()
                
                self._Commit()
                
                self._BeginImmediate()
                
                self._transaction_contains_writes = False
                
            else:
                
                self._Save()
                
            
            self._DoAfterJobWork()
            
            if job.IsSynchronous():
                
                job.PutResult( result )
                
            
        except Exception as e:
            
            self._ManageDBError( job, e )
            
            try:
                
                self._Rollback()
                
            except Exception as rollback_e:
                
                HydrusData.Print( 'When the transaction failed, attempting to rollback the database failed. Please restart the client as soon as is convenient.' )
                
                self._in_transaction = False
                
                self._CloseDBCursor()
                
                self._InitDBCursor()
                
                HydrusData.PrintException( rollback_e )
                
            
        finally:
            
            self._CleanAfterJobWork()
            
            self._current_status = ''
            
            self.publish_status_update()
            
        
    
    def _Read( self, action, *args, **kwargs ):
        
        raise NotImplementedError()
        
    
    def _RepairDB( self ):
        
        pass
        
    
    def _ReportOverupdatedDB( self, version ):
        
        pass
        
    
    def _ReportUnderupdatedDB( self, version ):
        
        pass
        
    
    def _ReportStatus( self, text ):
        
        HydrusData.Print( text )
        
    
    def _Rollback( self ):
        
        if self._in_transaction:
            
            self._c.execute( 'ROLLBACK TO hydrus_savepoint;' )
            
        else:
            
            HydrusData.Print( 'Received a call to rollback, but was not in a transaction!' )
            
        
    
    def _Save( self ):
        
        self._c.execute( 'RELEASE hydrus_savepoint;' )
        
        self._c.execute( 'SAVEPOINT hydrus_savepoint;' )
        
    
    def _ShrinkMemory( self ):
        
        self._c.execute( 'PRAGMA shrink_memory;' )
        
    
    def _STI( self, iterable_cursor ):
        
        # strip singleton tuples to an iterator
        
        return ( item for ( item, ) in iterable_cursor )
        
    
    def _STL( self, iterable_cursor ):
        
        # strip singleton tuples to a list
        
        return [ item for ( item, ) in iterable_cursor ]
        
    
    def _STS( self, iterable_cursor ):
        
        # strip singleton tuples to a set
        
        return { item for ( item, ) in iterable_cursor }
        
    
    def _TableHasAtLeastRowCount( self, name, row_count ):
        
        cursor = self._c.execute( 'SELECT 1 FROM {};'.format( name ) )
        
        for i in range( row_count ):
            
            r = cursor.fetchone()
            
            if r is None:
                
                return False
                
            
        
        return True
        
    
    def _TableIsEmpty( self, name ):
        
        result = self._c.execute( 'SELECT 1 FROM {};'.format( name ) )
        
        return result is None
        
    
    def _UpdateDB( self, version ):
        
        raise NotImplementedError()
        
    
    def _Write( self, action, *args, **kwargs ):
        
        raise NotImplementedError()
        
    
    def pub_after_job( self, topic, *args, **kwargs ):
        
        if len( args ) == 0 and len( kwargs ) == 0:
            
            if ( topic, args, kwargs ) in self._pubsubs:
                
                return
                
            
        
        self._pubsubs.append( ( topic, args, kwargs ) )
        
    
    def publish_status_update( self ):
        
        pass
        
    
    def CurrentlyDoingJob( self ):
        
        return self._currently_doing_job
        
    
    def GetApproxTotalFileSize( self ):
        
        total = 0
        
        for filename in list(self._db_filenames.values()):
            
            path = os.path.join( self._db_dir, filename )
            
            total += os.path.getsize( path )
            
        
        return total
        
    
    def GetSSLPaths( self ):
        
        # create ssl keys
        
        cert_here = os.path.exists( self._ssl_cert_path )
        key_here = os.path.exists( self._ssl_key_path )
        
        if cert_here ^ key_here:
            
            raise Exception( 'While creating the server database, only one of the paths "{}" and "{}" existed. You can create a db with these files already in place, but please either delete the existing file (to have hydrus generate its own pair) or find the other in the pair (to use your own).'.format( self._ssl_cert_path, self._ssl_key_path ) )
            
        elif not ( cert_here or key_here ):
            
            HydrusData.Print( 'Generating new cert/key files.' )
            
            HydrusEncryption.GenerateOpenSSLCertAndKeyFile( self._ssl_cert_path, self._ssl_key_path )
            
        
        return ( self._ssl_cert_path, self._ssl_key_path )
        
    
    def GetStatus( self ):
        
        return ( self._current_status, self._current_job_name )
        
    
    def IsDBUpdated( self ):
        
        return self._is_db_updated
        
    
    def IsFirstStart( self ):
        
        return self._is_first_start
        
    
    def LoopIsFinished( self ):
        
        return self._loop_finished
        
    
    def JobsQueueEmpty( self ):
        
        return self._jobs.empty()
        
    
    def MainLoop( self ):
        
        try:
            
            self._InitDBCursor() # have to reinitialise because the thread id has changed
            
            self._InitCaches()
            
        except:
            
            self._DisplayCatastrophicError( traceback.format_exc() )
            
            self._could_not_initialise = True
            
            return
            
        
        self._ready_to_serve_requests = True
        
        error_count = 0
        
        while not ( ( self._local_shutdown or HG.model_shutdown ) and self._jobs.empty() ):
            
            try:
                
                job = self._jobs.get( timeout = 1 )
                
                self._currently_doing_job = True
                self._current_job_name = job.ToString()
                
                self.publish_status_update()
                
                try:
                    
                    if HG.db_report_mode:
                        
                        summary = 'Running ' + job.ToString()
                        
                        HydrusData.ShowText( summary )
                        
                    
                    if HG.db_profile_mode:
                        
                        summary = 'Profiling ' + job.ToString()
                        
                        HydrusData.Profile( summary, 'self._ProcessJob( job )', globals(), locals(), show_summary = True )
                        
                    else:
                        
                        self._ProcessJob( job )
                        
                    
                    error_count = 0
                    
                except:
                    
                    error_count += 1
                    
                    if error_count > 5:
                        
                        raise
                        
                    
                    self._jobs.put( job ) # couldn't lock db; put job back on queue
                    
                    time.sleep( 5 )
                    
                
                self._currently_doing_job = False
                self._current_job_name = ''
                
                self.publish_status_update()
                
            except queue.Empty:
                
                if self._transaction_contains_writes and HydrusData.TimeHasPassed( self._transaction_started + self.TRANSACTION_COMMIT_TIME ):
                    
                    self._Commit()
                    
                    self._BeginImmediate()
                    
                    self._transaction_contains_writes = False
                    
                
            
            if self._pause_and_disconnect:
                
                self._CloseDBCursor()
                
                while self._pause_and_disconnect:
                    
                    if self._local_shutdown or HG.model_shutdown:
                        
                        break
                        
                    
                    time.sleep( 1 )
                    
                
                self._InitDBCursor()
                
            
        
        self._CleanUpCaches()
        
        self._CloseDBCursor()
        
        temp_path = os.path.join( self._db_dir, self._durable_temp_db_filename )
        
        HydrusPaths.DeletePath( temp_path )
        
        self._loop_finished = True
        
    
    def PauseAndDisconnect( self, pause_and_disconnect ):
        
        self._pause_and_disconnect = pause_and_disconnect
        
    
    def Read( self, action, *args, **kwargs ):
        
        if action in self.READ_WRITE_ACTIONS:
            
            job_type = 'read_write'
            
        else:
            
            job_type = 'read'
            
        
        synchronous = True
        
        job = self._GenerateDBJob( job_type, synchronous, action, *args, **kwargs )
        
        if HG.model_shutdown:
            
            raise HydrusExceptions.ShutdownException( 'Application has shut down!' )
            
        
        self._jobs.put( job )
        
        return job.GetResult()
        
    
    def ReadyToServeRequests( self ):
        
        return self._ready_to_serve_requests
        
    
    def Shutdown( self ):
        
        self._local_shutdown = True
        
    
    def Write( self, action, synchronous, *args, **kwargs ):
        
        job_type = 'write'
        
        job = self._GenerateDBJob( job_type, synchronous, action, *args, **kwargs )
        
        if HG.model_shutdown:
            
            raise HydrusExceptions.ShutdownException( 'Application has shut down!' )
            
        
        self._jobs.put( job )
        
        if synchronous: return job.GetResult()
        
    
class TemporaryIntegerTableNameCache( object ):
    
    my_instance = None
    
    def __init__( self ):
        
        TemporaryIntegerTableNameCache.my_instance = self
        
        self._column_names_to_table_names = collections.defaultdict( collections.deque )
        self._column_names_counter = collections.Counter()
        
    
    @staticmethod
    def instance() -> 'TemporaryIntegerTableNameCache':
        
        if TemporaryIntegerTableNameCache.my_instance is None:
            
            raise Exception( 'TemporaryIntegerTableNameCache is not yet initialised!' )
            
        else:
            
            return TemporaryIntegerTableNameCache.my_instance
            
        
    
    def Clear( self ):
        
        self._column_names_to_table_names = collections.defaultdict( collections.deque )
        self._column_names_counter = collections.Counter()
        
    
    def GetName( self, column_name ):
        
        table_names = self._column_names_to_table_names[ column_name ]
        
        initialised = True
        
        if len( table_names ) == 0:
            
            initialised = False
            
            i = self._column_names_counter[ column_name ]
            
            table_name = 'mem.temp_int_{}_{}'.format( column_name, i )
            
            table_names.append( table_name )
            
            self._column_names_counter[ column_name ] += 1
            
        
        table_name = table_names.pop()
        
        return ( initialised, table_name )
        
    
    def ReleaseName( self, column_name, table_name ):
        
        self._column_names_to_table_names[ column_name ].append( table_name )
        
    
class TemporaryIntegerTable( object ):
    
    def __init__( self, cursor, integer_iterable, column_name ):
        
        if not isinstance( integer_iterable, set ):
            
            integer_iterable = set( integer_iterable )
            
        
        self._cursor = cursor
        self._integer_iterable = integer_iterable
        self._column_name = column_name
        
        ( self._initialised, self._table_name ) = TemporaryIntegerTableNameCache.instance().GetName( self._column_name )
        
    
    def __enter__( self ):
        
        if not self._initialised:
            
            self._cursor.execute( 'CREATE TABLE {} ( {} INTEGER PRIMARY KEY );'.format( self._table_name, self._column_name ) )
            
        
        self._cursor.executemany( 'INSERT INTO {} ( {} ) VALUES ( ? );'.format( self._table_name, self._column_name ), ( ( i, ) for i in self._integer_iterable ) )
        
        return self._table_name
        
    
    def __exit__( self, exc_type, exc_val, exc_tb ):
        
        self._cursor.execute( 'DELETE FROM {};'.format( self._table_name ) )
        
        TemporaryIntegerTableNameCache.instance().ReleaseName( self._column_name, self._table_name )
        
        return False