LogicalTransactions in frontend Client #317
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| export PGPASSWORD=postgres | ||
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| docker-compose up -d | ||
| docker compose up -d |
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docker-compose is deprecated.
docker compose has replaced it.
docker-compose does not work on my recent version of docker desktop.
docker compose works on the version of docker in our CI.
win-win?
I suppose it will work for a every engineer's machine too. Can rollback this change if that is not the case
niclaflamme
changed the title
| prepared_statements: &mut PreparedStatements, | ||
| params: &Parameters, | ||
| in_transaction: bool, | ||
| logical_transaction: &LogicalTransaction, |
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this is the root change, followed the compiler from here basically.
pgdog/src/frontend/client/mod.rs
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| let in_transaction = self.in_transaction(); | ||
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| // 3) Reconcile against our LogicalTransaction | ||
| if should_be_tx && !in_transaction { |
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I'd probably clarify that the query parser isn't always active and therefore we don't catch BEGIN statements always. So sometimes, the only way to know we're inside a transaction is because the server told us.
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I think you're right, I also think it might be cheap to check twice. I'll check 👀
| Some(Command::StartTransaction(query)) => { | ||
| if let BufferedQuery::Query(_) = query { | ||
| self.start_transaction().await?; | ||
| inner.start_transaction = Some(query.clone()); |
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This is important to record. BEGIN can have multiple arguments that affect what kind of transaction we're starting: https://www.postgresql.org/docs/current/sql-begin.html
| /// Execute a BEGIN on all servers | ||
| /// TODO: Block mutli-shard BEGINs as transaction should not occur on multiple shards | ||
| pub async fn begin(&mut self) -> Result<(), Error> { | ||
| let query = Query::new("BEGIN"); |
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See other comment. Client can pass options to BEGIN, changing transaction type.
Replace the dead-simple in_transaction flag with a real LogicalTransaction state machine
Why
LogicalTransactionstruct carries that context.What changed
Refresher on logical transactions
Merge as standalone file in PR #313: a logical transaction makes a sharded cluster look like a single Postgres instance.
Basically, single-node postgres have Transactions.
PgDog can only have LogicalTransacion, and must orchestrate true Transactions across shards.
It tracks shards, phases, and errors early so we can later block illegal cross-shard writes and bolt on 2PC enventually.
TODO
LogicalTransaction::touch() is wired to throw if the client tries to touch multiple shards in the same txn (might need to track backend_ids instead—TBD). It’s not used yet; hook it up next.