fix: Avoid retaining buffer for latest parse in reader (#3533)

* test: Add failing test for parser reader cleanup

* fix: Avoid retaining buffer for latest parse in reader

The buffer can be arbitrarily large, and the parser shouldn’t keep it around while waiting on (and potentially also buffering) the next complete packet.

Author: charmander

packages/pg-protocol/src/inbound-parser.test.ts

@@ -4,6 +4,7 @@ import { parse } from '.'
 import assert from 'assert'
 import { PassThrough } from 'stream'
 import { BackendMessage } from './messages'
+import { Parser } from './parser'
 
 const authOkBuffer = buffers.authenticationOk()
 const paramStatusBuffer = buffers.parameterStatus('client_encoding', 'UTF8')
@@ -565,4 +566,10 @@ describe('PgPacketStream', function () {
       })
     })
   })
+
+  it('cleans up the reader after handling a packet', function () {
+    const parser = new Parser()
+    parser.parse(oneFieldBuf, () => {})
+    assert.strictEqual((parser as any).reader.buffer.byteLength, 0)
+  })
 })