feat(bigquery): add timestamp precision support to schema (#13421)

towards internal b/447623020

Author: shollyman

bigquery/schema.go

@@ -157,6 +157,12 @@ type FieldSchema struct {
 	// values of NUMERIC and BIGNUMERIC type.
 	// If unspecified, default value is RoundHalfAwayFromZero.
 	RoundingMode RoundingMode
+
+	// Precision (maximum number of total digits in
+	// base 10) for seconds of TIMESTAMP type. Possible values include:
+	// * 6 (Default, for TIMESTAMP type with microsecond precision)
+	// * 12 (For TIMESTAMP type with picosecond precision)
+	TimestampPrecision int64
 }
 
 func (fs *FieldSchema) toBQ() *bq.TableFieldSchema {
@@ -174,6 +180,10 @@ func (fs *FieldSchema) toBQ() *bq.TableFieldSchema {
 		RoundingMode:           string(fs.RoundingMode),
 	}
 
+	if fs.TimestampPrecision > 0 {
+		tfs.TimestampPrecision = &fs.TimestampPrecision
+	}
+
 	if fs.Repeated {
 		tfs.Mode = "REPEATED"
 	} else if fs.Required {
@@ -261,6 +271,9 @@ func bqToFieldSchema(tfs *bq.TableFieldSchema) *FieldSchema {
 		RangeElementType:       bqToRangeElementType(tfs.RangeElementType),
 		RoundingMode:           RoundingMode(tfs.RoundingMode),
 	}
+	if tfs.TimestampPrecision != nil {
+		fs.TimestampPrecision = *tfs.TimestampPrecision
+	}
 
 	for _, f := range tfs.Fields {
 		fs.Schema = append(fs.Schema, bqToFieldSchema(f))

bigquery/schema_test.go

@@ -249,6 +249,26 @@ func TestSchemaConversion(t *testing.T) {
 				fieldSchema("desc", "name", "TIMESTAMP", false, false, nil),
 			},
 		},
+		{
+			// Timestamp with precision
+			bqSchema: &bq.TableSchema{
+				Fields: []*bq.TableFieldSchema{
+					{
+						Description:        "desc",
+						Name:               "name",
+						Type:               "TIMESTAMP",
+						TimestampPrecision: int64ptr(12),
+					},
+				}},
+			schema: Schema{
+				{
+					Description:        "desc",
+					Name:               "name",
+					Type:               "TIMESTAMP",
+					TimestampPrecision: 12,
+				},
+			},
+		},
 		{
 			// civil times
 			bqSchema: &bq.TableSchema{

bigquery/table_integration_test.go

@@ -95,6 +95,7 @@ func TestIntegration_TableCreateWithConstraints(t *testing.T) {
 		{Name: "bytes_col", Type: BytesFieldType, MaxLength: 150},
 		{Name: "num_col", Type: NumericFieldType, Precision: 20},
 		{Name: "bignumeric_col", Type: BigNumericFieldType, Precision: 30, Scale: 5},
+		{Name: "timestamp_col", Type: TimestampFieldType, TimestampPrecision: 12},
 	}
 	err := table.Create(context.Background(), &TableMetadata{
 		Schema:         schema,

bigquery/value.go

@@ -28,6 +28,9 @@ import (
 	bq "google.golang.org/api/bigquery/v2"
 )
 
+// Utility functions to deal with byproducts of wrapper types in discovery.
+func int64ptr(v int64) *int64 { return &v }
+
 // Value stores the contents of a single cell from a BigQuery result.
 type Value interface{}