From e3185517424c7903d80cb24b789db2b702a736ce Mon Sep 17 00:00:00 2001
From: Joseph Buchma <josephbuchma@gmail.com>
Date: Mon, 27 Nov 2017 21:12:22 +0200
Subject: [PATCH] Flag for disabling milliseconds time resolution support

This change allows to restore v1.2 behavior of
dealing with time.Time values.

When connection is open with `disableMilliseconds=true`
time.Time values will be rounded DOWN to second resolution
before insert into database.
---
 connection.go |  5 +++++
 driver.go     |  1 +
 dsn.go        | 17 +++++++++++++++++
 3 files changed, 23 insertions(+)

diff --git a/connection.go b/connection.go
index e57061412..eb26af735 100644
--- a/connection.go
+++ b/connection.go
@@ -41,6 +41,8 @@ type mysqlConn struct {
 	sequence         uint8
 	parseTime        bool
 
+	disableMilliseconds bool
+
 	// for context support (Go 1.8+)
 	watching bool
 	watcher  chan<- mysqlContext
@@ -231,6 +233,9 @@ func (mc *mysqlConn) interpolateParams(query string, args []driver.Value) (strin
 			if v.IsZero() {
 				buf = append(buf, "'0000-00-00'"...)
 			} else {
+				if mc.disableMilliseconds {
+					v = v.Round(time.Second)
+				}
 				v := v.In(mc.cfg.Loc)
 				v = v.Add(time.Nanosecond * 500) // To round under microsecond
 				year := v.Year()
diff --git a/driver.go b/driver.go
index d42ce7a3d..ba47da09c 100644
--- a/driver.go
+++ b/driver.go
@@ -64,6 +64,7 @@ func (d MySQLDriver) Open(dsn string) (driver.Conn, error) {
 		return nil, err
 	}
 	mc.parseTime = mc.cfg.ParseTime
+	mc.disableMilliseconds = mc.cfg.DisableMilliseconds
 
 	// Connect to Server
 	if dial, ok := dials[mc.cfg.Net]; ok {
diff --git a/dsn.go b/dsn.go
index f5ea0d470..a7659ffc1 100644
--- a/dsn.go
+++ b/dsn.go
@@ -56,6 +56,7 @@ type Config struct {
 	InterpolateParams       bool // Interpolate placeholders into query string
 	MultiStatements         bool // Allow multiple statements in one query
 	ParseTime               bool // Parse time values to time.Time
+	DisableMilliseconds     bool // Disable DATETIME sub-second precision and round time.Time down.
 	RejectReadOnly          bool // Reject read-only connections
 }
 
@@ -226,6 +227,15 @@ func (cfg *Config) FormatDSN() string {
 		}
 	}
 
+	if cfg.DisableMilliseconds {
+		if hasParam {
+			buf.WriteString("&disableMilliseconds=true")
+		} else {
+			hasParam = true
+			buf.WriteString("?disableMilliseconds=true")
+		}
+	}
+
 	if cfg.ReadTimeout > 0 {
 		if hasParam {
 			buf.WriteString("&readTimeout=")
@@ -488,6 +498,13 @@ func parseDSNParams(cfg *Config, params string) (err error) {
 				return errors.New("invalid bool value: " + value)
 			}
 
+		case "disableMilliseconds":
+			var isBool bool
+			cfg.DisableMilliseconds, isBool = readBool(value)
+			if !isBool {
+				return errors.New("invalid bool value: " + value)
+			}
+
 		// I/O read Timeout
 		case "readTimeout":
 			cfg.ReadTimeout, err = time.ParseDuration(value)