DM-24355: make Database.sync (and methods that use it) transaction-friendly. #391
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TallJimbo
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timj
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Oct 9, 2020
| def ensure(self, table: sqlalchemy.schema.Table, *rows: dict) -> int: | ||
| # Docstring inherited. | ||
| if not (self.isWriteable() or table.key in self._tempTables): | ||
| raise ReadOnlyDatabaseError(f"Attempt to esnure into read-only database '{self}'.") |
| @@ -417,6 +433,17 @@ def replace(self, table: sqlalchemy.schema.Table, *rows: dict) -> None: | |||
| ) | |||
| self._connection.execute(_Replace(table), *rows) | |||
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| def ensure(self, table: sqlalchemy.schema.Table, *rows: dict) -> int: | |||
| if not (self.isWriteable() or table.key in self._tempTables): | |||
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This check is starting to appear in many places. Could we instead do something like a
self.assertWriteable(table)with an optional message string?
| @@ -65,15 +65,16 @@ class _Replace(sqlalchemy.sql.Insert): | |||
| pass | |||
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| # SQLite and PostgreSQL use similar syntax for their ON CONFLICT extension, | |||
| # but SQLAlchemy only knows about PostgreSQL's, so we have to compile some | |||
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That seems odd that sqlite doesn't support it in sqlalchemy. Is it just that sqlalchemy team haven't got around to it or there are problems with it? Could we submit a patch?
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I think it's slightly new functionality in SQLite, but not that new. I imagine a patch would be appreciated, but it'd be a while before I got around to it.
...or whatever that database engine's equivalent is (PostgreSQL and SQLite both use ON CONFLICT DO NOTHING). This is a pretty straightforward variant of the existing replace() implementations, but while it's usable in its own right, my main goal is to use it to make sync transaction-friendly in a future commit.
The new implementation uses more engine-specific functionality - namely the new ensure() method and table locking - but it's much simpler, and the most importantly it can now be used inside transactions, which will be huge for making higher-level operations idempotent.
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