[DB] Use Postgres startup encoding without SET NAMES

.github/workflows/compatibility.yaml

@@ -2,12 +2,23 @@ name: Postgres rustls compatibility
 on:
   push:
     branches: [gitar-0.6.11]
+  pull_request:
+    branches: [gitar-0.6.11]
   workflow_dispatch:
 permissions:
   contents: read
 jobs:
   postgres-tls:
-    runs-on: namespace-profile-gitar
+    runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:17
+        env:
+          POSTGRES_PASSWORD: fixture-password
+        ports: [5432:5432]
+        options: --health-cmd pg_isready --health-interval 5s --health-timeout 5s --health-retries 12
+    env:
+      TEST_PSQL: postgres://postgres:fixture-password@127.0.0.1:5432/postgres
     steps:
       - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
@@ -19,6 +30,9 @@ jobs:
             . -> target
             tests/rustls -> target
       - run: cargo check --locked --no-default-features --features postgresql,pooled,json,uuid,chrono,bigdecimal
+      - run: cargo fmt --check
+      - run: cargo test --locked --lib --no-default-features --features postgresql,pooled,json,uuid,chrono,bigdecimal startup_encoding_preserves_unicode_round_trips
+      - run: cargo test --locked --lib --no-default-features --features postgresql,pooled,json,uuid,chrono,bigdecimal test_custom_search_path
       - run: cargo clippy --locked --manifest-path tests/rustls/Cargo.toml --all-targets
       - run: python3 tests/rustls/run.py
       - name: Verify Postgres dependency tree has no native TLS or OpenSSL

.github/workflows/test.yml

@@ -4,6 +4,7 @@ on:
     branches:
       - main
   pull_request:
+    branches: [main]
 jobs:
   clippy:
     runs-on: ubuntu-latest

GITAR.md

@@ -8,6 +8,8 @@ System roots and PEM roots supplied with `sslcert` remain supported. `sslidentit
 
 Consumers must repeat both Cargo patch tables from this manifest at their workspace root. Cargo ignores patches in dependencies. The registry patch makes `tokio-postgres-rustls` use the same driver source as Quaint.
 
+PostgreSQL text encoding comes from tokio-postgres's UTF8 startup parameter. Connection initialization retains an explicit schema's search path and omits redundant `SET NAMES`, as that command pins sessions in RDS Proxy.
+
 Run `python3 tests/rustls/run.py` with Docker and OpenSSL 3 to exercise certificate verification and SCRAM channel binding. The runner also covers client identities and TLS negotiation. Set `OPENSSL_BIN` if OpenSSL 3 is not the default executable.
 
 Release tested source with immutable tags and pin consumers by commit. CLI binaries and checksums belong to the compatible `gitarcode/prisma-client-rust` release, which consumes this fork. Downloaded Prisma engine executables are separate artifacts and do not inherit this source change.

src/connector/postgres.rs

@@ -461,19 +461,12 @@ impl PostgreSql {
             }
         }));
 
-        // SET NAMES sets the client text encoding. It needs to be explicitly set for automatic
-        // conversion to and from UTF-8 to happen server-side.
-        //
-        // Relevant docs: https://www.postgresql.org/docs/current/multibyte.html
-        let session_variables = format!(
-            r##"
-            {set_search_path}
-            SET NAMES 'UTF8';
-            "##,
-            set_search_path = SetSearchPath(url.query_params.schema.as_deref())
-        );
-
-        client.simple_query(session_variables.as_str()).await?;
+        // tokio-postgres requests UTF8 in the startup packet. Repeating it with
+        // SET NAMES pins every RDS Proxy session to one database connection.
+        let session_variables = SetSearchPath(url.query_params.schema.as_deref()).to_string();
+        if !session_variables.is_empty() {
+            client.simple_query(session_variables.as_str()).await?;
+        }
 
         Ok(Self {
             client: PostgresClient(client),
@@ -833,6 +826,23 @@ mod tests {
         assert_eq!(Some("\"musti-test\""), row[0].as_str());
     }
 
+    #[tokio::test]
+    async fn startup_encoding_preserves_unicode_round_trips() -> crate::Result<()> {
+        let client = Quaint::new(&CONN_STR).await?;
+        let encoding = client.query_raw("SHOW client_encoding", &[]).await?;
+        assert_eq!(
+            encoding.first().and_then(|row| row[0].as_str().map(str::to_owned)),
+            Some("UTF8".to_string())
+        );
+        let text = "caf\u{00e9} \u{65e5}\u{672c}\u{8a9e}";
+        let result = client.query_raw("SELECT $1::text", &[text.into()]).await?;
+        assert_eq!(
+            result.first().and_then(|row| row[0].as_str().map(str::to_owned)),
+            Some(text.to_string())
+        );
+        Ok(())
+    }
+
     #[tokio::test]
     async fn should_map_nonexisting_database_error() {
         let mut url = Url::parse(&CONN_STR).unwrap();