# -*- coding: utf-8 -*- # Copyright 2014, 2015 OpenMarket Ltd # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import logging from synapse.api.errors import StoreError from synapse.util.logutils import log_function from synapse.util.logcontext import preserve_context_over_fn, LoggingContext from synapse.util.lrucache import LruCache from synapse.util.dictionary_cache import DictionaryCache import synapse.metrics from util.id_generators import IdGenerator, StreamIdGenerator from twisted.internet import defer from collections import namedtuple, OrderedDict import functools import inspect import sys import time import threading DEBUG_CACHES = False logger = logging.getLogger(__name__) sql_logger = logging.getLogger("synapse.storage.SQL") transaction_logger = logging.getLogger("synapse.storage.txn") perf_logger = logging.getLogger("synapse.storage.TIME") metrics = synapse.metrics.get_metrics_for("synapse.storage") sql_scheduling_timer = metrics.register_distribution("schedule_time") sql_query_timer = metrics.register_distribution("query_time", labels=["verb"]) sql_txn_timer = metrics.register_distribution("transaction_time", labels=["desc"]) caches_by_name = {} cache_counter = metrics.register_cache( "cache", lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()}, labels=["name"], ) class Cache(object): def __init__(self, name, max_entries=1000, keylen=1, lru=True): if lru: self.cache = LruCache(max_size=max_entries) self.max_entries = None else: self.cache = OrderedDict() self.max_entries = max_entries self.name = name self.keylen = keylen self.sequence = 0 self.thread = None caches_by_name[name] = self.cache class Sentinel(object): __slots__ = [] self.sentinel = Sentinel() def check_thread(self): expected_thread = self.thread if expected_thread is None: self.thread = threading.current_thread() else: if expected_thread is not threading.current_thread(): raise ValueError( "Cache objects can only be accessed from the main thread" ) def get(self, *keyargs): try: if len(keyargs) != self.keylen: raise ValueError("Expected a key to have %d items", self.keylen) val = self.cache.get(keyargs, self.sentinel) if val is not self.sentinel: cache_counter.inc_hits(self.name) return val cache_counter.inc_misses(self.name) raise KeyError() except KeyError: raise except: logger.exception("Cache.get failed for %s" % (self.name,)) raise def update(self, sequence, *args): try: self.check_thread() if self.sequence == sequence: # Only update the cache if the caches sequence number matches the # number that the cache had before the SELECT was started (SYN-369) self.prefill(*args) except: logger.exception("Cache.update failed for %s" % (self.name,)) raise def prefill(self, *args): # because I can't *keyargs, value keyargs = args[:-1] value = args[-1] if len(keyargs) != self.keylen: raise ValueError("Expected a key to have %d items", self.keylen) if self.max_entries is not None: while len(self.cache) >= self.max_entries: self.cache.popitem(last=False) self.cache[keyargs] = value def invalidate(self, *keyargs): self.check_thread() if len(keyargs) != self.keylen: raise ValueError("Expected a key to have %d items", self.keylen) # Increment the sequence number so that any SELECT statements that # raced with the INSERT don't update the cache (SYN-369) self.sequence += 1 self.cache.pop(keyargs, None) def invalidate_all(self): self.check_thread() self.sequence += 1 self.cache.clear() class CacheDescriptor(object): """ A method decorator that applies a memoizing cache around the function. The function is presumed to take zero or more arguments, which are used in a tuple as the key for the cache. Hits are served directly from the cache; misses use the function body to generate the value. The wrapped function has an additional member, a callable called "invalidate". This can be used to remove individual entries from the cache. The wrapped function has another additional callable, called "prefill", which can be used to insert values into the cache specifically, without calling the calculation function. """ def __init__(self, orig, max_entries=1000, num_args=1, lru=True, inlineCallbacks=False): self.orig = orig if inlineCallbacks: self.function_to_call = defer.inlineCallbacks(orig) else: self.function_to_call = orig self.max_entries = max_entries self.num_args = num_args self.lru = lru self.arg_names = inspect.getargspec(orig).args[1:num_args+1] if len(self.arg_names) < self.num_args: raise Exception( "Not enough explicit positional arguments to key off of for %r." " (@cached cannot key off of *args or **kwars)" % (orig.__name__,) ) def __get__(self, obj, objtype=None): cache = Cache( name=self.orig.__name__, max_entries=self.max_entries, keylen=self.num_args, lru=self.lru, ) @functools.wraps(self.orig) @defer.inlineCallbacks def wrapped(*args, **kwargs): arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs) keyargs = [arg_dict[arg_nm] for arg_nm in self.arg_names] try: cached_result = cache.get(*keyargs) if DEBUG_CACHES: actual_result = yield self.function_to_call(obj, *args, **kwargs) if actual_result != cached_result: logger.error( "Stale cache entry %s%r: cached: %r, actual %r", self.orig.__name__, keyargs, cached_result, actual_result, ) raise ValueError("Stale cache entry") defer.returnValue(cached_result) except KeyError: # Get the sequence number of the cache before reading from the # database so that we can tell if the cache is invalidated # while the SELECT is executing (SYN-369) sequence = cache.sequence ret = yield self.function_to_call(obj, *args, **kwargs) cache.update(sequence, *(keyargs + [ret])) defer.returnValue(ret) wrapped.invalidate = cache.invalidate wrapped.invalidate_all = cache.invalidate_all wrapped.prefill = cache.prefill obj.__dict__[self.orig.__name__] = wrapped return wrapped def cached(max_entries=1000, num_args=1, lru=True): return lambda orig: CacheDescriptor( orig, max_entries=max_entries, num_args=num_args, lru=lru ) def cachedInlineCallbacks(max_entries=1000, num_args=1, lru=False): return lambda orig: CacheDescriptor( orig, max_entries=max_entries, num_args=num_args, lru=lru, inlineCallbacks=True, ) class LoggingTransaction(object): """An object that almost-transparently proxies for the 'txn' object passed to the constructor. Adds logging and metrics to the .execute() method.""" __slots__ = ["txn", "name", "database_engine", "after_callbacks"] def __init__(self, txn, name, database_engine, after_callbacks): object.__setattr__(self, "txn", txn) object.__setattr__(self, "name", name) object.__setattr__(self, "database_engine", database_engine) object.__setattr__(self, "after_callbacks", after_callbacks) def call_after(self, callback, *args): """Call the given callback on the main twisted thread after the transaction has finished. Used to invalidate the caches on the correct thread. """ self.after_callbacks.append((callback, args)) def __getattr__(self, name): return getattr(self.txn, name) def __setattr__(self, name, value): setattr(self.txn, name, value) def execute(self, sql, *args): self._do_execute(self.txn.execute, sql, *args) def executemany(self, sql, *args): self._do_execute(self.txn.executemany, sql, *args) def _do_execute(self, func, sql, *args): # TODO(paul): Maybe use 'info' and 'debug' for values? sql_logger.debug("[SQL] {%s} %s", self.name, sql) sql = self.database_engine.convert_param_style(sql) if args: try: sql_logger.debug( "[SQL values] {%s} %r", self.name, args[0] ) except: # Don't let logging failures stop SQL from working pass start = time.time() * 1000 try: return func( sql, *args ) except Exception as e: logger.debug("[SQL FAIL] {%s} %s", self.name, e) raise finally: msecs = (time.time() * 1000) - start sql_logger.debug("[SQL time] {%s} %f", self.name, msecs) sql_query_timer.inc_by(msecs, sql.split()[0]) class PerformanceCounters(object): def __init__(self): self.current_counters = {} self.previous_counters = {} def update(self, key, start_time, end_time=None): if end_time is None: end_time = time.time() * 1000 duration = end_time - start_time count, cum_time = self.current_counters.get(key, (0, 0)) count += 1 cum_time += duration self.current_counters[key] = (count, cum_time) return end_time def interval(self, interval_duration, limit=3): counters = [] for name, (count, cum_time) in self.current_counters.items(): prev_count, prev_time = self.previous_counters.get(name, (0, 0)) counters.append(( (cum_time - prev_time) / interval_duration, count - prev_count, name )) self.previous_counters = dict(self.current_counters) counters.sort(reverse=True) top_n_counters = ", ".join( "%s(%d): %.3f%%" % (name, count, 100 * ratio) for ratio, count, name in counters[:limit] ) return top_n_counters class SQLBaseStore(object): _TXN_ID = 0 def __init__(self, hs): self.hs = hs self._db_pool = hs.get_db_pool() self._clock = hs.get_clock() self._previous_txn_total_time = 0 self._current_txn_total_time = 0 self._previous_loop_ts = 0 # TODO(paul): These can eventually be removed once the metrics code # is running in mainline, and we have some nice monitoring frontends # to watch it self._txn_perf_counters = PerformanceCounters() self._get_event_counters = PerformanceCounters() self._get_event_cache = Cache("*getEvent*", keylen=3, lru=True, max_entries=hs.config.event_cache_size) self._state_group_cache = DictionaryCache("*stateGroupCache*", 100000) self._event_fetch_lock = threading.Condition() self._event_fetch_list = [] self._event_fetch_ongoing = 0 self._pending_ds = [] self.database_engine = hs.database_engine self._stream_id_gen = StreamIdGenerator("events", "stream_ordering") self._transaction_id_gen = IdGenerator("sent_transactions", "id", self) self._state_groups_id_gen = IdGenerator("state_groups", "id", self) self._access_tokens_id_gen = IdGenerator("access_tokens", "id", self) self._pushers_id_gen = IdGenerator("pushers", "id", self) self._push_rule_id_gen = IdGenerator("push_rules", "id", self) self._push_rules_enable_id_gen = IdGenerator("push_rules_enable", "id", self) self._receipts_id_gen = StreamIdGenerator("receipts_linearized", "stream_id") def start_profiling(self): self._previous_loop_ts = self._clock.time_msec() def loop(): curr = self._current_txn_total_time prev = self._previous_txn_total_time self._previous_txn_total_time = curr time_now = self._clock.time_msec() time_then = self._previous_loop_ts self._previous_loop_ts = time_now ratio = (curr - prev)/(time_now - time_then) top_three_counters = self._txn_perf_counters.interval( time_now - time_then, limit=3 ) top_3_event_counters = self._get_event_counters.interval( time_now - time_then, limit=3 ) perf_logger.info( "Total database time: %.3f%% {%s} {%s}", ratio * 100, top_three_counters, top_3_event_counters ) self._clock.looping_call(loop, 10000) def _new_transaction(self, conn, desc, after_callbacks, func, *args, **kwargs): start = time.time() * 1000 txn_id = self._TXN_ID # We don't really need these to be unique, so lets stop it from # growing really large. self._TXN_ID = (self._TXN_ID + 1) % (sys.maxint - 1) name = "%s-%x" % (desc, txn_id, ) transaction_logger.debug("[TXN START] {%s}", name) try: i = 0 N = 5 while True: try: txn = conn.cursor() txn = LoggingTransaction( txn, name, self.database_engine, after_callbacks ) r = func(txn, *args, **kwargs) conn.commit() return r except self.database_engine.module.OperationalError as e: # This can happen if the database disappears mid # transaction. logger.warn( "[TXN OPERROR] {%s} %s %d/%d", name, e, i, N ) if i < N: i += 1 try: conn.rollback() except self.database_engine.module.Error as e1: logger.warn( "[TXN EROLL] {%s} %s", name, e1, ) continue raise except self.database_engine.module.DatabaseError as e: if self.database_engine.is_deadlock(e): logger.warn("[TXN DEADLOCK] {%s} %d/%d", name, i, N) if i < N: i += 1 try: conn.rollback() except self.database_engine.module.Error as e1: logger.warn( "[TXN EROLL] {%s} %s", name, e1, ) continue raise except Exception as e: logger.debug("[TXN FAIL] {%s} %s", name, e) raise finally: end = time.time() * 1000 duration = end - start transaction_logger.debug("[TXN END] {%s} %f", name, duration) self._current_txn_total_time += duration self._txn_perf_counters.update(desc, start, end) sql_txn_timer.inc_by(duration, desc) @defer.inlineCallbacks def runInteraction(self, desc, func, *args, **kwargs): """Wraps the .runInteraction() method on the underlying db_pool.""" current_context = LoggingContext.current_context() start_time = time.time() * 1000 after_callbacks = [] def inner_func(conn, *args, **kwargs): with LoggingContext("runInteraction") as context: sql_scheduling_timer.inc_by(time.time() * 1000 - start_time) if self.database_engine.is_connection_closed(conn): logger.debug("Reconnecting closed database connection") conn.reconnect() current_context.copy_to(context) return self._new_transaction( conn, desc, after_callbacks, func, *args, **kwargs ) result = yield preserve_context_over_fn( self._db_pool.runWithConnection, inner_func, *args, **kwargs ) for after_callback, after_args in after_callbacks: after_callback(*after_args) defer.returnValue(result) @defer.inlineCallbacks def runWithConnection(self, func, *args, **kwargs): """Wraps the .runInteraction() method on the underlying db_pool.""" current_context = LoggingContext.current_context() start_time = time.time() * 1000 def inner_func(conn, *args, **kwargs): with LoggingContext("runWithConnection") as context: sql_scheduling_timer.inc_by(time.time() * 1000 - start_time) if self.database_engine.is_connection_closed(conn): logger.debug("Reconnecting closed database connection") conn.reconnect() current_context.copy_to(context) return func(conn, *args, **kwargs) result = yield preserve_context_over_fn( self._db_pool.runWithConnection, inner_func, *args, **kwargs ) defer.returnValue(result) def cursor_to_dict(self, cursor): """Converts a SQL cursor into an list of dicts. Args: cursor : The DBAPI cursor which has executed a query. Returns: A list of dicts where the key is the column header. """ col_headers = list(column[0] for column in cursor.description) results = list( dict(zip(col_headers, row)) for row in cursor.fetchall() ) return results def _execute(self, desc, decoder, query, *args): """Runs a single query for a result set. Args: decoder - The function which can resolve the cursor results to something meaningful. query - The query string to execute *args - Query args. Returns: The result of decoder(results) """ def interaction(txn): txn.execute(query, args) if decoder: return decoder(txn) else: return txn.fetchall() return self.runInteraction(desc, interaction) def _execute_and_decode(self, desc, query, *args): return self._execute(desc, self.cursor_to_dict, query, *args) # "Simple" SQL API methods that operate on a single table with no JOINs, # no complex WHERE clauses, just a dict of values for columns. @defer.inlineCallbacks def _simple_insert(self, table, values, or_ignore=False, desc="_simple_insert"): """Executes an INSERT query on the named table. Args: table : string giving the table name values : dict of new column names and values for them """ try: yield self.runInteraction( desc, self._simple_insert_txn, table, values, ) except self.database_engine.module.IntegrityError: # We have to do or_ignore flag at this layer, since we can't reuse # a cursor after we receive an error from the db. if not or_ignore: raise @log_function def _simple_insert_txn(self, txn, table, values): keys, vals = zip(*values.items()) sql = "INSERT INTO %s (%s) VALUES(%s)" % ( table, ", ".join(k for k in keys), ", ".join("?" for _ in keys) ) txn.execute(sql, vals) def _simple_insert_many_txn(self, txn, table, values): if not values: return # This is a *slight* abomination to get a list of tuples of key names # and a list of tuples of value names. # # i.e. [{"a": 1, "b": 2}, {"c": 3, "d": 4}] # => [("a", "b",), ("c", "d",)] and [(1, 2,), (3, 4,)] # # The sort is to ensure that we don't rely on dictionary iteration # order. keys, vals = zip(*[ zip( *(sorted(i.items(), key=lambda kv: kv[0])) ) for i in values if i ]) for k in keys: if k != keys[0]: raise RuntimeError( "All items must have the same keys" ) sql = "INSERT INTO %s (%s) VALUES(%s)" % ( table, ", ".join(k for k in keys[0]), ", ".join("?" for _ in keys[0]) ) txn.executemany(sql, vals) def _simple_upsert(self, table, keyvalues, values, insertion_values={}, desc="_simple_upsert", lock=True): """ Args: table (str): The table to upsert into keyvalues (dict): The unique key tables and their new values values (dict): The nonunique columns and their new values insertion_values (dict): key/values to use when inserting Returns: A deferred """ return self.runInteraction( desc, self._simple_upsert_txn, table, keyvalues, values, insertion_values, lock ) def _simple_upsert_txn(self, txn, table, keyvalues, values, insertion_values={}, lock=True): # We need to lock the table :(, unless we're *really* careful if lock: self.database_engine.lock_table(txn, table) # Try to update sql = "UPDATE %s SET %s WHERE %s" % ( table, ", ".join("%s = ?" % (k,) for k in values), " AND ".join("%s = ?" % (k,) for k in keyvalues) ) sqlargs = values.values() + keyvalues.values() logger.debug( "[SQL] %s Args=%s", sql, sqlargs, ) txn.execute(sql, sqlargs) if txn.rowcount == 0: # We didn't update and rows so insert a new one allvalues = {} allvalues.update(keyvalues) allvalues.update(values) allvalues.update(insertion_values) sql = "INSERT INTO %s (%s) VALUES (%s)" % ( table, ", ".join(k for k in allvalues), ", ".join("?" for _ in allvalues) ) logger.debug( "[SQL] %s Args=%s", sql, keyvalues.values(), ) txn.execute(sql, allvalues.values()) def _simple_select_one(self, table, keyvalues, retcols, allow_none=False, desc="_simple_select_one"): """Executes a SELECT query on the named table, which is expected to return a single row, returning a single column from it. Args: table : string giving the table name keyvalues : dict of column names and values to select the row with retcols : list of strings giving the names of the columns to return allow_none : If true, return None instead of failing if the SELECT statement returns no rows """ return self.runInteraction( desc, self._simple_select_one_txn, table, keyvalues, retcols, allow_none, ) def _simple_select_one_onecol(self, table, keyvalues, retcol, allow_none=False, desc="_simple_select_one_onecol"): """Executes a SELECT query on the named table, which is expected to return a single row, returning a single column from it." Args: table : string giving the table name keyvalues : dict of column names and values to select the row with retcol : string giving the name of the column to return """ return self.runInteraction( desc, self._simple_select_one_onecol_txn, table, keyvalues, retcol, allow_none=allow_none, ) def _simple_select_one_onecol_txn(self, txn, table, keyvalues, retcol, allow_none=False): ret = self._simple_select_onecol_txn( txn, table=table, keyvalues=keyvalues, retcol=retcol, ) if ret: return ret[0] else: if allow_none: return None else: raise StoreError(404, "No row found") def _simple_select_onecol_txn(self, txn, table, keyvalues, retcol): sql = ( "SELECT %(retcol)s FROM %(table)s WHERE %(where)s" ) % { "retcol": retcol, "table": table, "where": " AND ".join("%s = ?" % k for k in keyvalues.keys()), } txn.execute(sql, keyvalues.values()) return [r[0] for r in txn.fetchall()] def _simple_select_onecol(self, table, keyvalues, retcol, desc="_simple_select_onecol"): """Executes a SELECT query on the named table, which returns a list comprising of the values of the named column from the selected rows. Args: table (str): table name keyvalues (dict): column names and values to select the rows with retcol (str): column whos value we wish to retrieve. Returns: Deferred: Results in a list """ return self.runInteraction( desc, self._simple_select_onecol_txn, table, keyvalues, retcol ) def _simple_select_list(self, table, keyvalues, retcols, desc="_simple_select_list"): """Executes a SELECT query on the named table, which may return zero or more rows, returning the result as a list of dicts. Args: table : string giving the table name keyvalues : dict of column names and values to select the rows with, or None to not apply a WHERE clause. retcols : list of strings giving the names of the columns to return """ return self.runInteraction( desc, self._simple_select_list_txn, table, keyvalues, retcols ) def _simple_select_list_txn(self, txn, table, keyvalues, retcols): """Executes a SELECT query on the named table, which may return zero or more rows, returning the result as a list of dicts. Args: txn : Transaction object table : string giving the table name keyvalues : dict of column names and values to select the rows with retcols : list of strings giving the names of the columns to return """ if keyvalues: sql = "SELECT %s FROM %s WHERE %s" % ( ", ".join(retcols), table, " AND ".join("%s = ?" % (k, ) for k in keyvalues) ) txn.execute(sql, keyvalues.values()) else: sql = "SELECT %s FROM %s" % ( ", ".join(retcols), table ) txn.execute(sql) return self.cursor_to_dict(txn) def _simple_update_one(self, table, keyvalues, updatevalues, desc="_simple_update_one"): """Executes an UPDATE query on the named table, setting new values for columns in a row matching the key values. Args: table : string giving the table name keyvalues : dict of column names and values to select the row with updatevalues : dict giving column names and values to update retcols : optional list of column names to return If present, retcols gives a list of column names on which to perform a SELECT statement *before* performing the UPDATE statement. The values of these will be returned in a dict. These are performed within the same transaction, allowing an atomic get-and-set. This can be used to implement compare-and-set by putting the update column in the 'keyvalues' dict as well. """ return self.runInteraction( desc, self._simple_update_one_txn, table, keyvalues, updatevalues, ) def _simple_update_one_txn(self, txn, table, keyvalues, updatevalues): update_sql = "UPDATE %s SET %s WHERE %s" % ( table, ", ".join("%s = ?" % (k,) for k in updatevalues), " AND ".join("%s = ?" % (k,) for k in keyvalues) ) txn.execute( update_sql, updatevalues.values() + keyvalues.values() ) if txn.rowcount == 0: raise StoreError(404, "No row found") if txn.rowcount > 1: raise StoreError(500, "More than one row matched") def _simple_select_one_txn(self, txn, table, keyvalues, retcols, allow_none=False): select_sql = "SELECT %s FROM %s WHERE %s" % ( ", ".join(retcols), table, " AND ".join("%s = ?" % (k,) for k in keyvalues) ) txn.execute(select_sql, keyvalues.values()) row = txn.fetchone() if not row: if allow_none: return None raise StoreError(404, "No row found") if txn.rowcount > 1: raise StoreError(500, "More than one row matched") return dict(zip(retcols, row)) def _simple_selectupdate_one(self, table, keyvalues, updatevalues=None, retcols=None, allow_none=False, desc="_simple_selectupdate_one"): """ Combined SELECT then UPDATE.""" def func(txn): ret = None if retcols: ret = self._simple_select_one_txn( txn, table=table, keyvalues=keyvalues, retcols=retcols, allow_none=allow_none, ) if updatevalues: self._simple_update_one_txn( txn, table=table, keyvalues=keyvalues, updatevalues=updatevalues, ) # if txn.rowcount == 0: # raise StoreError(404, "No row found") if txn.rowcount > 1: raise StoreError(500, "More than one row matched") return ret return self.runInteraction(desc, func) def _simple_delete_one(self, table, keyvalues, desc="_simple_delete_one"): """Executes a DELETE query on the named table, expecting to delete a single row. Args: table : string giving the table name keyvalues : dict of column names and values to select the row with """ sql = "DELETE FROM %s WHERE %s" % ( table, " AND ".join("%s = ?" % (k, ) for k in keyvalues) ) def func(txn): txn.execute(sql, keyvalues.values()) if txn.rowcount == 0: raise StoreError(404, "No row found") if txn.rowcount > 1: raise StoreError(500, "more than one row matched") return self.runInteraction(desc, func) def _simple_delete(self, table, keyvalues, desc="_simple_delete"): """Executes a DELETE query on the named table. Args: table : string giving the table name keyvalues : dict of column names and values to select the row with """ return self.runInteraction(desc, self._simple_delete_txn) def _simple_delete_txn(self, txn, table, keyvalues): sql = "DELETE FROM %s WHERE %s" % ( table, " AND ".join("%s = ?" % (k, ) for k in keyvalues) ) return txn.execute(sql, keyvalues.values()) def _simple_max_id(self, table): """Executes a SELECT query on the named table, expecting to return the max value for the column "id". Args: table : string giving the table name """ sql = "SELECT MAX(id) AS id FROM %s" % table def func(txn): txn.execute(sql) max_id = self.cursor_to_dict(txn)[0]["id"] if max_id is None: return 0 return max_id return self.runInteraction("_simple_max_id", func) def get_next_stream_id(self): with self._next_stream_id_lock: i = self._next_stream_id self._next_stream_id += 1 return i class _RollbackButIsFineException(Exception): """ This exception is used to rollback a transaction without implying something went wrong. """ pass class Table(object): """ A base class used to store information about a particular table. """ table_name = None """ str: The name of the table """ fields = None """ list: The field names """ EntryType = None """ Type: A tuple type used to decode the results """ _select_where_clause = "SELECT %s FROM %s WHERE %s" _select_clause = "SELECT %s FROM %s" _insert_clause = "REPLACE INTO %s (%s) VALUES (%s)" @classmethod def select_statement(cls, where_clause=None): """ Args: where_clause (str): The WHERE clause to use. Returns: str: An SQL statement to select rows from the table with the given WHERE clause. """ if where_clause: return cls._select_where_clause % ( ", ".join(cls.fields), cls.table_name, where_clause ) else: return cls._select_clause % ( ", ".join(cls.fields), cls.table_name, ) @classmethod def insert_statement(cls): return cls._insert_clause % ( cls.table_name, ", ".join(cls.fields), ", ".join(["?"] * len(cls.fields)), ) @classmethod def decode_single_result(cls, results): """ Given an iterable of tuples, return a single instance of `EntryType` or None if the iterable is empty Args: results (list): The results list to convert to `EntryType` Returns: EntryType: An instance of `EntryType` """ results = list(results) if results: return cls.EntryType(*results[0]) else: return None @classmethod def decode_results(cls, results): """ Given an iterable of tuples, return a list of `EntryType` Args: results (list): The results list to convert to `EntryType` Returns: list: A list of `EntryType` """ return [cls.EntryType(*row) for row in results] @classmethod def get_fields_string(cls, prefix=None): if prefix: to_join = ("%s.%s" % (prefix, f) for f in cls.fields) else: to_join = cls.fields return ", ".join(to_join) class JoinHelper(object): """ Used to help do joins on tables by looking at the tables' fields and creating a list of unique fields to use with SELECTs and a namedtuple to dump the results into. Attributes: tables (list): List of `Table` classes EntryType (type) """ def __init__(self, *tables): self.tables = tables res = [] for table in self.tables: res += [f for f in table.fields if f not in res] self.EntryType = namedtuple("JoinHelperEntry", res) def get_fields(self, **prefixes): """Get a string representing a list of fields for use in SELECT statements with the given prefixes applied to each. For example:: JoinHelper(PdusTable, StateTable).get_fields( PdusTable="pdus", StateTable="state" ) """ res = [] for field in self.EntryType._fields: for table in self.tables: if field in table.fields: res.append("%s.%s" % (prefixes[table.__name__], field)) break return ", ".join(res) def decode_results(self, rows): return [self.EntryType(*row) for row in rows]