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Check that auto_vacuum
is disabled when porting a SQLite database to Postgres, as VACUUM
s must not be performed between runs of the script. (#13195)
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changelog.d/13195.misc
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changelog.d/13195.misc
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Check that `auto_vacuum` is disabled when porting a SQLite database to Postgres, as `VACUUM`s must not be performed between runs of the script.
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@ -143,6 +143,14 @@ to do step 2.
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It is safe to at any time kill the port script and restart it.
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However, under no circumstances should the SQLite database be `VACUUM`ed between
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multiple runs of the script. Doing so can lead to an inconsistent copy of your database
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into Postgres.
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To avoid accidental error, the script will check that SQLite's `auto_vacuum` mechanism
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is disabled, but the script is not able to protect against a manual `VACUUM` operation
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performed either by the administrator or by any automated task that the administrator
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may have configured.
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Note that the database may take up significantly more (25% - 100% more)
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space on disk after porting to Postgres.
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@ -621,6 +621,25 @@ class Porter:
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self.postgres_store.db_pool.updates.has_completed_background_updates()
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)
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@staticmethod
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def _is_sqlite_autovacuum_enabled(txn: LoggingTransaction) -> bool:
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"""
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Returns true if auto_vacuum is enabled in SQLite.
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https://www.sqlite.org/pragma.html#pragma_auto_vacuum
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Vacuuming changes the rowids on rows in the database.
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Auto-vacuuming is therefore dangerous when used in conjunction with this script.
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Note that the auto_vacuum setting can't be changed without performing
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a VACUUM after trying to change the pragma.
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"""
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txn.execute("PRAGMA auto_vacuum")
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row = txn.fetchone()
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assert row is not None, "`PRAGMA auto_vacuum` did not give a row."
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(autovacuum_setting,) = row
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# 0 means off. 1 means full. 2 means incremental.
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return autovacuum_setting != 0
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async def run(self) -> None:
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"""Ports the SQLite database to a PostgreSQL database.
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@ -637,6 +656,21 @@ class Porter:
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allow_outdated_version=True,
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)
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# For safety, ensure auto_vacuums are disabled.
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if await self.sqlite_store.db_pool.runInteraction(
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"is_sqlite_autovacuum_enabled", self._is_sqlite_autovacuum_enabled
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):
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end_error = (
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"auto_vacuum is enabled in the SQLite database."
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" (This is not the default configuration.)\n"
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" This script relies on rowids being consistent and must not"
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" be used if the database could be vacuumed between re-runs.\n"
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" To disable auto_vacuum, you need to stop Synapse and run the following SQL:\n"
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" PRAGMA auto_vacuum=off;\n"
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" VACUUM;"
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)
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return
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# Check if all background updates are done, abort if not.
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updates_complete = (
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await self.sqlite_store.db_pool.updates.has_completed_background_updates()
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