feat: support ancient mysql versions (5.0+)

sqlx-core/src/mysql/connection/establish.rs

@@ -2,7 +2,9 @@ use bytes::Bytes;
 
 use crate::common::StatementCache;
 use crate::error::Error;
-use crate::mysql::connection::{tls, MySqlStream, COLLATE_UTF8MB4_UNICODE_CI, MAX_PACKET_SIZE};
+use crate::mysql::connection::{
+    tls, MySqlStream, COLLATE_UTF8MB4_UNICODE_CI, COLLATE_UTF8_UNICODE_CI, MAX_PACKET_SIZE,
+};
 use crate::mysql::protocol::connect::{
     AuthSwitchRequest, AuthSwitchResponse, Handshake, HandshakeResponse,
 };
@@ -22,6 +24,35 @@ impl MySqlConnection {
         let mut plugin = handshake.auth_plugin;
         let mut nonce = handshake.auth_plugin_data;
 
+        // FIXME: server version parse is a bit ugly
+        // expecting MAJOR.MINOR.PATCH
+
+        let mut server_version = handshake.server_version.split('.');
+
+        let server_version_major: u16 = server_version
+            .next()
+            .unwrap_or_default()
+            .parse()
+            .unwrap_or(0);
+
+        let server_version_minor: u16 = server_version
+            .next()
+            .unwrap_or_default()
+            .parse()
+            .unwrap_or(0);
+
+        let server_version_patch: u16 = server_version
+            .next()
+            .unwrap_or_default()
+            .parse()
+            .unwrap_or(0);
+
+        stream.server_version = (
+            server_version_major,
+            server_version_minor,
+            server_version_patch,
+        );
+
         stream.capabilities &= handshake.server_capabilities;
         stream.capabilities |= Capabilities::PROTOCOL_41;
 
@@ -39,8 +70,14 @@ impl MySqlConnection {
             None
         };
 
+        let char_set = if stream.server_version >= (5, 5, 3) {
+            COLLATE_UTF8MB4_UNICODE_CI
+        } else {
+            COLLATE_UTF8_UNICODE_CI
+        };
+
         stream.write_packet(HandshakeResponse {
-            char_set: COLLATE_UTF8MB4_UNICODE_CI,
+            char_set,
             max_packet_size: MAX_PACKET_SIZE,
             username: &options.username,
             database: options.database.as_deref(),

sqlx-core/src/mysql/connection/mod.rs

@@ -22,7 +22,8 @@ mod tls;
 use crate::transaction::Transaction;
 pub(crate) use stream::{Busy, MySqlStream};
 
-const COLLATE_UTF8MB4_UNICODE_CI: u8 = 224;
+pub(crate) const COLLATE_UTF8_UNICODE_CI: u8 = 192;
+pub(crate) const COLLATE_UTF8MB4_UNICODE_CI: u8 = 224;
 
 const MAX_PACKET_SIZE: u32 = 1024;
 

sqlx-core/src/mysql/connection/stream.rs

@@ -12,6 +12,7 @@ use crate::net::{MaybeTlsStream, Socket};
 
 pub struct MySqlStream {
     stream: BufStream<MaybeTlsStream<Socket>>,
+    pub(crate) server_version: (u16, u16, u16),
     pub(super) capabilities: Capabilities,
     pub(crate) sequence_id: u8,
     pub(crate) busy: Busy,
@@ -55,6 +56,7 @@ impl MySqlStream {
         Ok(Self {
             busy: Busy::NotBusy,
             capabilities,
+            server_version: (0, 0, 0),
             sequence_id: 0,
             stream: BufStream::new(MaybeTlsStream::Raw(socket)),
         })

sqlx-core/src/mysql/options/connect.rs

@@ -39,11 +39,19 @@ impl ConnectOptions for MySqlConnectOptions {
 
             // https://mathiasbynens.be/notes/mysql-utf8mb4
 
-            conn.execute(concat!(
+            let mut options = String::new();
-                r#"SET sql_mode=(SELECT CONCAT(@@sql_mode, ',PIPES_AS_CONCAT,NO_ENGINE_SUBSTITUTION')),"#,
+            options.push_str(r#"SET sql_mode=(SELECT CONCAT(@@sql_mode, ',PIPES_AS_CONCAT,NO_ENGINE_SUBSTITUTION')),"#);
-                r#"time_zone='+00:00',"#,
+            options.push_str(r#"time_zone='+00:00',"#);
-                r#"NAMES utf8mb4 COLLATE utf8mb4_unicode_ci;"#,
+
-            )).await?;
+            let char_set = if conn.stream.server_version >= (5, 5, 3) {
+                "utf8mb4"
+            } else {
+                "utf8"
+            };
+
+            options.push_str(&format!(r#"NAMES {0} COLLATE {0}_unicode_ci;"#, char_set));
+
+            conn.execute(&*options).await?;
 
             Ok(conn)
         })

sqlx-core/src/mysql/types/str.rs

@@ -1,6 +1,7 @@
 use crate::decode::Decode;
 use crate::encode::{Encode, IsNull};
 use crate::error::BoxDynError;
+use crate::mysql::connection::{COLLATE_UTF8MB4_UNICODE_CI, COLLATE_UTF8_UNICODE_CI};
 use crate::mysql::io::MySqlBufMutExt;
 use crate::mysql::protocol::text::{ColumnFlags, ColumnType};
 use crate::mysql::{MySql, MySqlTypeInfo, MySqlValueRef};
@@ -26,7 +27,8 @@ impl Type<MySql> for str {
                 | ColumnType::String
                 | ColumnType::VarString
                 | ColumnType::Enum
-        ) && ty.char_set == 224
+        ) && (ty.char_set == COLLATE_UTF8MB4_UNICODE_CI.into()
+            || ty.char_set == COLLATE_UTF8_UNICODE_CI.into())
     }
 }