From 4c3b3f5df20c768f836c029e4794980ecc20f052 Mon Sep 17 00:00:00 2001
From: Colin Adams <colin@recidiviz.org>
Date: Mon, 15 May 2023 10:03:08 -0700
Subject: [PATCH] Update format when casting datetimes to strings

---
 internal/encoder.go           | 28 ++++++++++++++++++++++++++-
 internal/function_datetime.go |  2 +-
 internal/function_time.go     |  4 ++--
 query_test.go                 | 36 +++++++++++++++++++++++++++++++++++
 4 files changed, 66 insertions(+), 4 deletions(-)

diff --git a/internal/encoder.go b/internal/encoder.go
index 3be191e..a4218bc 100644
--- a/internal/encoder.go
+++ b/internal/encoder.go
@@ -378,7 +378,25 @@ func CastValue(t types.Type, v Value) (Value, error) {
 			return nil, err
 		}
 		return FloatValue(f64), nil
-	case types.STRING, types.ENUM:
+	case types.STRING:
+		switch v.(type) {
+		// If this is coming from a date/time, the format is slightly different
+		// than when just writing the value out as a string.
+		case DateValue:
+			return convertTimeValueToStringWithFormat(v, "2006-01-02")
+		case DatetimeValue:
+			return convertTimeValueToStringWithFormat(v, "2006-01-02 15:04:05.999999")
+		case TimeValue:
+			return convertTimeValueToStringWithFormat(v, "15:04:05.999999")
+		case TimestampValue:
+			return convertTimeValueToStringWithFormat(v, "2006-01-02 15:04:05.999999-07")
+		}
+		s, err := v.ToString()
+		if err != nil {
+			return nil, err
+		}
+		return StringValue(s), nil
+	case types.ENUM:
 		s, err := v.ToString()
 		if err != nil {
 			return nil, err
@@ -507,6 +525,14 @@ func CastValue(t types.Type, v Value) (Value, error) {
 	return nil, fmt.Errorf("unsupported cast %s value", t.Kind())
 }
 
+func convertTimeValueToStringWithFormat(v Value, format string) (Value, error) {
+	valueTime, err := v.ToTime()
+	if err != nil {
+		return nil, err
+	}
+	return StringValue(valueTime.UTC().Format(format)), nil
+}
+
 func ValueFromGoValue(v interface{}) (Value, error) {
 	if isNullValue(v) {
 		return nil, nil
diff --git a/internal/function_datetime.go b/internal/function_datetime.go
index aaf525e..95fac0a 100644
--- a/internal/function_datetime.go
+++ b/internal/function_datetime.go
@@ -100,7 +100,7 @@ func DATETIME(args ...Value) (Value, error) {
 			}
 			return DatetimeValue(t.In(loc)), nil
 		}
-		return DatetimeValue(t), nil
+		return DatetimeValue(t.UTC()), nil
 	}
 	return nil, fmt.Errorf("DATETIME: first argument must be DATE or TIMESTAMP type")
 }
diff --git a/internal/function_time.go b/internal/function_time.go
index e0a291b..b9213e5 100644
--- a/internal/function_time.go
+++ b/internal/function_time.go
@@ -57,13 +57,13 @@ func TIME(args ...Value) (Value, error) {
 			}
 			return TimeValue(t.In(loc)), nil
 		}
-		return TimeValue(t), nil
+		return TimeValue(t.UTC()), nil
 	case DatetimeValue:
 		t, err := args[0].ToTime()
 		if err != nil {
 			return nil, err
 		}
-		return TimeValue(t), nil
+		return TimeValue(t.UTC()), nil
 	}
 	return nil, fmt.Errorf("TIME: invalid first argument type %T", args[0])
 }
diff --git a/query_test.go b/query_test.go
index 31d13f3..90bb831 100644
--- a/query_test.go
+++ b/query_test.go
@@ -3706,6 +3706,12 @@ SELECT date, EXTRACT(ISOYEAR FROM date), EXTRACT(YEAR FROM date), EXTRACT(MONTH
 			expectedRows: [][]interface{}{{"2008"}},
 		},
 
+		{
+			name:         "cast date as string",
+			query:        `SELECT CAST(DATE("2022-08-01 06:47:51.123456-07:00") AS STRING)`,
+			expectedRows: [][]interface{}{{"2022-08-01"}},
+		},
+
 		{
 			name:         "last_day",
 			query:        `SELECT LAST_DAY(DATE '2008-11-25') AS last_day`,
@@ -3876,6 +3882,16 @@ SELECT date, EXTRACT(ISOYEAR FROM date), EXTRACT(YEAR FROM date), EXTRACT(MONTH
 			query:        `SELECT FORMAT_DATETIME("%E4Y", DATETIME "2008-12-25 15:30:12.345678")`,
 			expectedRows: [][]interface{}{{"2008"}},
 		},
+		{
+			name:         "cast datetime as string",
+			query:        `SELECT CAST(DATETIME(TIMESTAMP("2022-08-01 06:47:51.123456-07:00")) AS STRING)`,
+			expectedRows: [][]interface{}{{"2022-08-01 13:47:51.123456"}},
+		},
+		{
+			name:         "cast date as datetime",
+			query:        `SELECT CAST(DATE("1987-01-25") AS DATETIME)`,
+			expectedRows: [][]interface{}{{"1987-01-25T00:00:00"}},
+		},
 		{
 			name:         "parse datetime",
 			query:        `SELECT PARSE_DATETIME("%a %b %e %I:%M:%S %Y", "Thu Dec 25 07:30:00 2008")`,
@@ -3952,6 +3968,21 @@ SELECT date, EXTRACT(ISOYEAR FROM date), EXTRACT(YEAR FROM date), EXTRACT(MONTH
 			query:        `SELECT FORMAT_TIME("%E*S", TIME "15:30:12.345678")`,
 			expectedRows: [][]interface{}{{"12.345678"}},
 		},
+		{
+			name:         "cast time as string",
+			query:        `SELECT CAST(TIME("2022-08-01 06:47:51.123456-04:00") AS STRING)`,
+			expectedRows: [][]interface{}{{"10:47:51.123456"}},
+		},
+		{
+			name:         "cast time with timezone as string",
+			query:        `SELECT CAST(TIME("2022-08-01 06:47:51.123456-04:00", "America/Los_Angeles") AS STRING)`,
+			expectedRows: [][]interface{}{{"03:47:51.123456"}},
+		},
+		{
+			name:         "cast time from datetime as string",
+			query:        `SELECT CAST(TIME(DATETIME(TIMESTAMP("2022-08-01 06:47:51.123456-04:00"))) AS STRING)`,
+			expectedRows: [][]interface{}{{"10:47:51.123456"}},
+		},
 		{
 			name:         "parse time with %I:%M:%S",
 			query:        `SELECT PARSE_TIME("%I:%M:%S", "07:30:00")`,
@@ -4094,6 +4125,11 @@ SELECT date, EXTRACT(ISOYEAR FROM date), EXTRACT(YEAR FROM date), EXTRACT(MONTH
 			query:        `SELECT FORMAT_TIMESTAMP("%Ez", TIMESTAMP "2008-12-25 15:30:12.345678+00")`,
 			expectedRows: [][]interface{}{{"+00:00"}},
 		},
+		{
+			name:         "cast timestamp as string",
+			query:        `SELECT CAST(TIMESTAMP("2022-08-01 06:47:51.123456-07:00") AS STRING);`,
+			expectedRows: [][]interface{}{{"2022-08-01 13:47:51.123456+00"}},
+		},
 		{
 			name:         "parse timestamp with %a %b %e %I:%M:%S %Y",
 			query:        `SELECT PARSE_TIMESTAMP("%a %b %e %I:%M:%S %Y", "Thu Dec 25 07:30:00 2008")`,