Follow up to #12701, which introduced a new regression. When profiling
locally I noticed that writes have the tendency to always reallocate. On
investigation I found that even if the `Connection`'s write buffer is
empty, if it still shares the same data pointer as the `Client`'s write
buffer then the client cannot reclaim it.
The best way I found to fix this is to just drop the `Connection`'s
write buffer each time we fully flush it.
Additionally, I remembered that `BytesMut` has an `unsplit` method which
is allows even better sharing over the previous optimisation I had when
'encoding'.
## Problem
A large insert or a large row will cause the codec to allocate a large
buffer. The codec never shrinks the buffer however. LKB-2496
## Summary of changes
1. Introduce a naive GC system for codec buffers
2. Try and reduce copies as much as possible
A replacement for #10254 which allows us to introduce notice messages
for sql-over-http in the future if we want to. This also removes the
`ParameterStatus` and `Notification` handling as there's nothing we
could/should do for those.
## Problem
For #11992 I realised we need to get the type info before executing the
query. This is important to know how to decode rows with custom types,
eg the following query:
```sql
CREATE TYPE foo AS ENUM ('foo','bar','baz');
SELECT ARRAY['foo'::foo, 'bar'::foo, 'baz'::foo] AS data;
```
Getting that to work was harder that it seems. The original
tokio-postgres setup has a split between `Client` and `Connection`,
where messages are passed between. Because multiple clients were
supported, each client message included a dedicated response channel.
Each request would be terminated by the `ReadyForQuery` message.
The flow I opted to use for parsing types early would not trigger a
`ReadyForQuery`. The flow is as follows:
```
PARSE "" // parse the user provided query
DESCRIBE "" // describe the query, returning param/result type oids
FLUSH // force postgres to flush the responses early
// wait for descriptions
// check if we know the types, if we don't then
// setup the typeinfo query and execute it against each OID:
PARSE typeinfo // prepare our typeinfo query
DESCRIBE typeinfo
FLUSH // force postgres to flush the responses early
// wait for typeinfo statement
// for each OID we don't know:
BIND typeinfo
EXECUTE
FLUSH
// wait for type info, might reveal more OIDs to inspect
// close the typeinfo query, we cache the OID->type map and this is kinder to pgbouncer.
CLOSE typeinfo
// finally once we know all the OIDs:
BIND "" // bind the user provided query - already parsed - to the user provided params
EXECUTE // run the user provided query
SYNC // commit the transaction
```
## Summary of changes
Please review commit by commit. The main challenge was allowing one
query to issue multiple sub-queries. To do this I first made sure that
the client could fully own the connection, which required removing any
shared client state. I then had to replace the way responses are sent to
the client, by using only a single permanent channel. This required some
additional effort to track which query is being processed. Lastly I had
to modify the query/typeinfo functions to not issue `sync` commands, so
it would fit into the desired flow above.
To note: the flow above does force an extra roundtrip into each query. I
don't know yet if this has a measurable latency overhead.
This upgrades the `proxy/` crate as well as the forked libraries in
`libs/proxy/` to edition 2024.
Also reformats the imports of those forked libraries via:
```
cargo +nightly fmt -p proxy -p postgres-protocol2 -p postgres-types2 -p tokio-postgres2 -- -l --config imports_granularity=Module,group_imports=StdExternalCrate,reorder_imports=true
```
It can be read commit-by-commit: the first commit has no formatting
changes, only changes to accomodate the new edition.
Part of #10918
(stacked on #9990 and #9995)
Partially fixes#1287 with a custom option field to enable the fixed
behaviour. This allows us to gradually roll out the fix without silently
changing the observed behaviour for our customers.
related to https://github.com/neondatabase/cloud/issues/15284
Our rust-postgres fork is getting messy. Mostly because proxy wants more
control over the raw protocol than tokio-postgres provides. As such,
it's diverging more and more. Storage and compute also make use of
rust-postgres, but in more normal usage, thus they don't need our crazy
changes.
Idea:
* proxy maintains their subset
* other teams use a minimal patch set against upstream rust-postgres
Reviewing this code will be difficult. To implement it, I
1. Copied tokio-postgres, postgres-protocol and postgres-types from
00940fcdb5
2. Updated their package names with the `2` suffix to make them compile
in the workspace.
3. Updated proxy to use those packages
4. Copied in the code from tokio-postgres-rustls 0.13 (with some patches
applied https://github.com/jbg/tokio-postgres-rustls/pull/32https://github.com/jbg/tokio-postgres-rustls/pull/33)
5. Removed as much dead code as I could find in the vendored libraries
6. Updated the tokio-postgres-rustls code to use our existing channel
binding implementation
