Truncate logged strings and byte slices

conn.go

@@ -569,9 +569,9 @@ func (c *Conn) Exec(sql string, arguments ...interface{}) (commandTag CommandTag
 	defer func() {
 		if err == nil {
 			endTime := time.Now()
-			c.logger.Info("Exec", "sql", sql, "args", arguments, "time", endTime.Sub(startTime), "commandTag", commandTag)
+			c.logger.Info("Exec", "sql", sql, "args", logQueryArgs(arguments), "time", endTime.Sub(startTime), "commandTag", commandTag)
 		} else {
-			c.logger.Error("Exec", "sql", sql, "args", arguments, "error", err)
+			c.logger.Error("Exec", "sql", sql, "args", logQueryArgs(arguments), "error", err)
 		}
 	}()
 

logger.go

@@ -1,5 +1,10 @@
 package pgx
 
+import (
+	"encoding/hex"
+	"fmt"
+)
+
 // Logger is the interface used to get logging from pgx internals.
 // https://github.com/inconshreveable/log15 is the recommended logging package.
 // This logging interface was extracted from there. However, it should be simple
@@ -43,3 +48,25 @@ func (l *connLogger) Error(msg string, ctx ...interface{}) {
 	ctx = append(ctx, "pid", l.pid)
 	l.logger.Error(msg, ctx...)
 }
+
+func logQueryArgs(args ...interface{}) []interface{} {
+	logArgs := make([]interface{}, 0, len(args))
+
+	for _, a := range args {
+		switch v := a.(type) {
+		case []byte:
+			if len(v) < 64 {
+				a = hex.EncodeToString(v)
+			} else {
+				a = fmt.Sprintf("%x (truncated %d bytes)", v[:64], len(v)-64)
+			}
+		case string:
+			if len(v) > 64 {
+				a = fmt.Sprintf("%s (truncated %d bytes)", v[:64], len(v)-64)
+			}
+		}
+		logArgs = append(logArgs, a)
+	}
+
+	return logArgs
+}

query.go

@@ -70,9 +70,9 @@ func (rows *Rows) close() {
 
 	if rows.err == nil {
 		endTime := time.Now()
-		rows.logger.Info("Query", "sql", rows.sql, "args", rows.args, "time", endTime.Sub(rows.startTime), "rowCount", rows.rowCount)
+		rows.logger.Info("Query", "sql", rows.sql, "args", logQueryArgs(rows.args), "time", endTime.Sub(rows.startTime), "rowCount", rows.rowCount)
 	} else {
-		rows.logger.Error("Query", "sql", rows.sql, "args", rows.args)
+		rows.logger.Error("Query", "sql", rows.sql, "args", logQueryArgs(rows.args))
 	}
 }