Use utf8mb4 by default

source/mysql/protocol/comms.d

@@ -21,6 +21,7 @@ Next tasks for this sub-package's cleanup:
 module mysql.protocol.comms;
 
 import std.algorithm;
+import std.array;
 import std.conv;
 import std.digest.sha;
 import std.exception;
@@ -45,7 +46,7 @@ package struct ProtocolPrepared
 	import std.datetime;
 	import std.variant;
 	import mysql.types;
-	
+
 	static ubyte[] makeBitmap(in Variant[] inParams)
 	{
 		size_t bml = (inParams.length+7)/8;
@@ -451,7 +452,7 @@ package struct ProtocolPrepared
 		Variant[] inParams, ParameterSpecialization[] psa)
 	{
 		conn.autoPurge();
-		
+
 		ubyte[] packet;
 		conn.resetPacket();
 
@@ -771,7 +772,7 @@ body
 	}
 
 	conn.autoPurge();
- 
+
 	conn.resetPacket();
 
 	ubyte[] header;
@@ -810,7 +811,7 @@ body
 	// Request a conventional maximum packet length.
 	1.packInto(packet[8..12]);
 
-	packet ~= 33; // Set UTF-8 as default charSet
+	packet ~= getDefaultCollation(conn._serverVersion);
 
 	// There's a statutory block of zero bytes here - fill them in.
 	foreach(i; 0 .. 23)
@@ -967,7 +968,7 @@ package(mysql) SvrCapFlags setClientFlags(SvrCapFlags serverCaps, SvrCapFlags ca
 	// didn't supply it
 	cCaps |= SvrCapFlags.PROTOCOL41;
 	cCaps |= SvrCapFlags.SECURE_CONNECTION;
-	
+
 	return cCaps;
 }
 
@@ -998,7 +999,7 @@ package(mysql) PreparedServerInfo performRegister(Connection conn, const(char[])
 	scope(failure) conn.kill();
 
 	PreparedServerInfo info;
-	
+
 	conn.sendCmd(CommandType.STMT_PREPARE, sql);
 	conn._fieldCount = 0;
 
@@ -1112,3 +1113,30 @@ package(mysql) void enableMultiStatements(Connection conn, bool on)
 	auto packet = conn.getPacket();
 	enforce!MYXProtocol(packet[0] == 254 && packet.length == 5, "Unexpected response to SET_OPTION command");
 }
+
+private ubyte getDefaultCollation(string serverVersion)
+{
+	// MySQL >= 5.5.3 supports utf8mb4
+	const v = serverVersion
+		.splitter('.')
+		.map!(a => a.parse!ushort)
+		.array;
+
+	if (v[0] < 5)
+		return 33; // Set utf8_general_ci as default
+	if (v[1] < 5)
+		return 33; // Set utf8_general_ci as default
+	if (v[2] < 3)
+		return 33; // Set utf8_general_ci as default
+
+	return 45; // Set utf8mb4_general_ci as default
+}
+
+unittest
+{
+	assert(getDefaultCollation("5.5.3") == 45);
+	assert(getDefaultCollation("5.5.2") == 33);
+
+	// MariaDB: https://mariadb.com/kb/en/connection/#initial-handshake-packet
+	assert(getDefaultCollation("5.5.5-10.0.7-MariaDB") == 45);
+}