[arrow] branch main updated: MINOR: [Go] Make `arrow.TimestampType.GetToTimeFunc` similar to `arrow.Timestamp.ToTime` (#37512)

[zeroshade]

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The following commit(s) were added to refs/heads/main by this push:
     new faa7cf6bcf MINOR: [Go] Make `arrow.TimestampType.GetToTimeFunc` 
similar to `arrow.Timestamp.ToTime` (#37512)
faa7cf6bcf is described below

commit faa7cf6bcf412677a379ca28fbbb5582c0715cb6
Author: Alex Shcherbakov <candidusl...@users.noreply.github.com>
AuthorDate: Fri Sep 1 18:41:28 2023 +0300

    MINOR: [Go] Make `arrow.TimestampType.GetToTimeFunc` similar to 
`arrow.Timestamp.ToTime` (#37512)
    
    ### Rationale for this change
    
    Follow-up for https://github.com/apache/arrow/pull/36964
    
    ### What changes are included in this PR?
    
    Make the `arrow.TimestampType.GetToTimeFunc` similar to 
`arrow.Timestamp.ToTime` in order not to get overflows.
    
    ### Are these changes tested?
    
    Yes
    
    ### Are there any user-facing changes?
    
    No.
    
    Authored-by: candiduslynx <candidusl...@gmail.com>
    Signed-off-by: Matt Topol <zotthewiz...@gmail.com>
---
 go/arrow/datatype_fixedwidth.go      | 14 ++++----------
 go/arrow/datatype_fixedwidth_test.go | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/go/arrow/datatype_fixedwidth.go b/go/arrow/datatype_fixedwidth.go
index f8806d25e2..7f62becdc2 100644
--- a/go/arrow/datatype_fixedwidth.go
+++ b/go/arrow/datatype_fixedwidth.go
@@ -374,9 +374,9 @@ func (t *TimestampType) Fingerprint() string {
 // BitWidth returns the number of bits required to store a single element of 
this data type in memory.
 func (*TimestampType) BitWidth() int { return 64 }
 
-func (TimestampType) Bytes() int { return Int64SizeBytes }
+func (*TimestampType) Bytes() int { return Int64SizeBytes }
 
-func (TimestampType) Layout() DataTypeLayout {
+func (*TimestampType) Layout() DataTypeLayout {
        return DataTypeLayout{Buffers: []BufferSpec{SpecBitmap(), 
SpecFixedWidth(TimestampSizeBytes)}}
 }
 
@@ -444,15 +444,9 @@ func (t *TimestampType) GetToTimeFunc() (func(Timestamp) 
time.Time, error) {
        case Second:
                return func(v Timestamp) time.Time { return time.Unix(int64(v), 
0).In(tz) }, nil
        case Millisecond:
-               factor := int64(time.Second / time.Millisecond)
-               return func(v Timestamp) time.Time {
-                       return time.Unix(int64(v)/factor, 
(int64(v)%factor)*int64(time.Millisecond)).In(tz)
-               }, nil
+               return func(v Timestamp) time.Time { return 
time.UnixMilli(int64(v)).In(tz) }, nil
        case Microsecond:
-               factor := int64(time.Second / time.Microsecond)
-               return func(v Timestamp) time.Time {
-                       return time.Unix(int64(v)/factor, 
(int64(v)%factor)*int64(time.Microsecond)).In(tz)
-               }, nil
+               return func(v Timestamp) time.Time { return 
time.UnixMicro(int64(v)).In(tz) }, nil
        case Nanosecond:
                return func(v Timestamp) time.Time { return time.Unix(0, 
int64(v)).In(tz) }, nil
        }
diff --git a/go/arrow/datatype_fixedwidth_test.go 
b/go/arrow/datatype_fixedwidth_test.go
index bf93f0fc61..1d3a07de09 100644
--- a/go/arrow/datatype_fixedwidth_test.go
+++ b/go/arrow/datatype_fixedwidth_test.go
@@ -166,6 +166,20 @@ func TestTimestampToTime(t *testing.T) {
        assert.Equal(t, "2345-12-30 00:00:00", tm.Format("2006-01-02 
15:04:05.999"))
 }
 
+func TestTimestampType_GetToTimeFunc(t *testing.T) {
+       typUTC := &arrow.TimestampType{Unit: arrow.Millisecond}
+       toTimeUTC, err := typUTC.GetToTimeFunc()
+       assert.NoError(t, err)
+
+       typNY := &arrow.TimestampType{Unit: arrow.Millisecond, TimeZone: 
"America/New_York"}
+       toTimeNY, err := typNY.GetToTimeFunc()
+       assert.NoError(t, err)
+
+       ts := arrow.Timestamp(11865225600000)
+       assert.Equal(t, "2345-12-30T00:00:00Z", 
toTimeUTC(ts).Format(time.RFC3339))
+       assert.Equal(t, "2345-12-29T19:00:00-05:00", 
toTimeNY(ts).Format(time.RFC3339))
+}
+
 func TestTime32Type(t *testing.T) {
        for _, tc := range []struct {
                unit arrow.TimeUnit