Conn: Improved extended query handling (#73)

* removed unnecessary write back to client

Signed-off-by: AmoebaProtozoa <8039876+AmoebaProtozoa@users.noreply.github.com>

* fixed extended query describe

Signed-off-by: AmoebaProtozoa <8039876+AmoebaProtozoa@users.noreply.github.com>

server/conn_stmt.go

@@ -89,11 +89,7 @@ func (cc *clientConn) handleStmtPrepare(ctx context.Context, parser pgproto3.Par
 
 	stmt.SetParamsType(paramTypes)
 
-	err = cc.writeParseComplete()
-	if err != nil {
-		return err
-	}
-	return cc.flush(ctx)
+	return cc.writeParseComplete()
 }
 
 // handleStmtBind handle bind messages in pgsql's extended query.
@@ -156,11 +152,7 @@ func (cc *clientConn) handleStmtBind(ctx context.Context, bind pgproto3.Bind) (e
 		vars.Portal["0"] = stmtID
 	}
 
-	err = cc.writeBindComplete()
-	if err != nil {
-		return err
-	}
-	return cc.flush(ctx)
+	return cc.writeBindComplete()
 }
 
 // handleStmtDescription handle Description messages in pgsql's extended query，
@@ -177,14 +169,17 @@ func (cc *clientConn) handleStmtDescription(ctx context.Context, desc pgproto3.D
 
 	var stmtID uint32
 	var ok bool
+	var isPortal bool
 
-	// If it specify the prepared statement through portal,
+	// If it specifies the prepared statement through portal,
 	// here can directly find the corresponding stmtID through portal.
 	if desc.ObjectType == 'P' {
 		stmtID, ok = vars.Portal[desc.Name]
+		isPortal = true
 	} else {
 		// Or get prepared stmtID through stmtName.
 		stmtID, ok = vars.PreparedStmtNameToID[desc.Name]
+		isPortal = false
 	}
 
 	if !ok {
@@ -199,12 +194,13 @@ func (cc *clientConn) handleStmtDescription(ctx context.Context, desc pgproto3.D
 			strconv.FormatUint(uint64(stmtID), 10), "stmt_description")
 	}
 
-	numParams := stmt.NumParams()
-	if numParams > 0 {
+	// we send parameter description only if this is statement and not a portal
+	// https://www.postgresql.org/docs/current/protocol-flow.html#PROTOCOL-FLOW-EXT-QUERY
+	if !isPortal {
 		// Get param types that analyzed in `handleStmtBind`,
 		// And convert it to PgSQL data type and return it to the client
 		paramsType := stmt.GetParamsType()
-		pgType := make([]uint32, numParams)
+		pgType := make([]uint32, stmt.NumParams())
 		for i := range paramsType {
 			pgType[i] = convertMySQLDataTypeToPgSQLDataType(paramsType[i])
 		}
@@ -218,18 +214,11 @@ func (cc *clientConn) handleStmtDescription(ctx context.Context, desc pgproto3.D
 	// otherwise return `writeNoData`.
 	columnInfo := stmt.GetColumnInfo()
 	if columnInfo == nil || len(columnInfo) > 0 {
-		if err := cc.WriteRowDescription(columnInfo); err != nil {
-			return err
-		}
-
-		// If the row description information has been output here,
-		// it will not be output when `writeResultset` later.
-	} else {
-		if err := cc.writeNoData(); err != nil {
-			return err
-		}
+		return cc.WriteRowDescription(columnInfo)
 	}
-	return cc.flush(ctx)
+	// If the row description information has been output here,
+	// it will not be output when `writeResultset` later.
+	return cc.writeNoData()
 }
 
 // handleStmtExecute handle execute messages in pgsql's extended query.