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authorKali Kaneko <kali@leap.se>2014-02-19 23:50:23 -0400
committerKali Kaneko <kali@leap.se>2014-02-20 00:21:31 -0400
commit2404b07cc015c4ce76425b7bcf1277a6bbfded64 (patch)
tree82e02473cf8ef90a8424a245d83f898f50281bfe /client
parent057e7c28f9fc790fa449cef5361fba9dcd5009d1 (diff)
Set Write-Ahead Logging
with autocommit set to 50 pages, a value that will permit fast reads. also set synchronous mode to normal on regular operation.
Diffstat (limited to 'client')
-rw-r--r--client/src/leap/soledad/client/sqlcipher.py45
1 files changed, 45 insertions, 0 deletions
diff --git a/client/src/leap/soledad/client/sqlcipher.py b/client/src/leap/soledad/client/sqlcipher.py
index d8ba0b79..09efa592 100644
--- a/client/src/leap/soledad/client/sqlcipher.py
+++ b/client/src/leap/soledad/client/sqlcipher.py
@@ -194,8 +194,11 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
cipher_page_size)
if os.environ.get('LEAP_SQLITE_NOSYNC'):
self._pragma_synchronous_off(self._db_handle)
+ else:
+ self._pragma_synchronous_normal(self._db_handle)
if os.environ.get('LEAP_SQLITE_MEMSTORE'):
self._pragma_mem_temp_store(self._db_handle)
+ self._pragma_write_ahead_logging(self._db_handle)
self._real_replica_uid = None
self._ensure_schema()
self._crypto = crypto
@@ -766,6 +769,14 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
db_handle.cursor().execute('PRAGMA synchronous=OFF')
@classmethod
+ def _pragma_synchronous_normal(cls, db_handle):
+ """
+ Change the setting of the "synchronous" flag to NORMAL.
+ """
+ logger.debug("SQLCIPHER: SETTING SYNCHRONOUS NORMAL")
+ db_handle.cursor().execute('PRAGMA synchronous=NORMAL')
+
+ @classmethod
def _pragma_mem_temp_store(cls, db_handle):
"""
Use a in-memory store for temporary tables.
@@ -773,6 +784,40 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
logger.debug("SQLCIPHER: SETTING TEMP_STORE MEMORY")
db_handle.cursor().execute('PRAGMA temp_store=MEMORY')
+ @classmethod
+ def _pragma_write_ahead_logging(cls, db_handle):
+ """
+ Enable write-ahead logging, and set the autocheckpoint to 50 pages.
+
+ Setting the autocheckpoint to a small value, we make the reads not
+ suffer too much performance degradation.
+
+ From the sqlite docs:
+
+ "There is a tradeoff between average read performance and average write
+ performance. To maximize the read performance, one wants to keep the
+ WAL as small as possible and hence run checkpoints frequently, perhaps
+ as often as every COMMIT. To maximize write performance, one wants to
+ amortize the cost of each checkpoint over as many writes as possible,
+ meaning that one wants to run checkpoints infrequently and let the WAL
+ grow as large as possible before each checkpoint. The decision of how
+ often to run checkpoints may therefore vary from one application to
+ another depending on the relative read and write performance
+ requirements of the application. The default strategy is to run a
+ checkpoint once the WAL reaches 1000 pages"
+ """
+ logger.debug("SQLCIPHER: SETTING WRITE-AHEAD LOGGING")
+ db_handle.cursor().execute('PRAGMA journal_mode=WAL')
+ # The optimum value can still use a little bit of tuning, but we favor
+ # small sizes of the WAL file to get fast reads, since we assume that
+ # the writes will be quick enough to not block too much.
+
+ # TODO
+ # As a further improvement, we might want to set autocheckpoint to 0
+ # here and do the checkpoints manually in a separate thread, to avoid
+ # any blocks in the main thread (we should run a loopingcall from here)
+ db_handle.cursor().execute('PRAGMA wal_autocheckpoint=50')
+
# Extra query methods: extensions to the base sqlite implmentation.
def get_count_from_index(self, index_name, *key_values):