sql: Add support for numeric JSON scalar casts

* Fixes cockroachdb#41333
* Add support for queries such as
  - `SELECT '1'::jsonb::int`
  - `SELECT '1'::jsonb::float`
  - `SELECT '3.14'::jsonb::decimal`

Release note: None

pkg/sql/sem/tree/eval.go

@@ -3213,6 +3213,18 @@ func PerformCast(ctx *EvalContext, d Datum, t *types.T) (Datum, error) {
  res = NewDInt(DInt(iv))
  case *DOid:
  res = &v.DInt
+ case *DJSON:
+ if v.Type() == json.NumberJSONType {
+ // err is ignored as a more appropriate error
+ // will be generated later
+ dec, err := json.ToDecimal(v.JSON)
+ if err == nil {
+ asInt, err := dec.Int64()
+ if err == nil {
+ res = NewDInt(DInt(asInt))
+ }
+ }
+ }
  }
  if res != nil {
  return res, nil
@@ -3253,6 +3265,18 @@ func PerformCast(ctx *EvalContext, d Datum, t *types.T) (Datum, error) {
  return NewDFloat(DFloat(float64(v.UnixEpochDays()))), nil
  case *DInterval:
  return NewDFloat(DFloat(v.AsFloat64())), nil
+ case *DJSON:
+ if v.Type() == json.NumberJSONType {
+ // err is ignored as a more appropriate error
+ // will be generated later
+ dec, err := json.ToDecimal(v.JSON)
+ if err == nil {
+ asFloat, err := dec.Int64()
+ if err == nil {
+ return NewDFloat(DFloat(asFloat)), nil
+ }
+ }
+ }
  }
 
  case types.DecimalFamily:
@@ -3301,6 +3325,15 @@ func PerformCast(ctx *EvalContext, d Datum, t *types.T) (Datum, error) {
  case *DInterval:
  v.AsBigInt(&dd.Coeff)
  dd.Exponent = -9
+ case *DJSON:
+ if v.Type() == json.NumberJSONType {
+ var dec apd.Decimal
+ // err is ignored as a more appropriate error
+ // will be generated later
+ dec, err = json.ToDecimal(v.JSON)
+ unset = err != nil
+ dd = DDecimal{dec}
+ }
  default:
  unset = true
  }

pkg/sql/sem/tree/expr.go

@@ -1520,11 +1520,11 @@ var (
  bitArrayCastTypes = annotateCast(types.VarBit, []*types.T{types.Unknown, types.VarBit, types.Int, types.String, types.AnyCollatedString})
  boolCastTypes = annotateCast(types.Bool, []*types.T{types.Unknown, types.Bool, types.Int, types.Float, types.Decimal, types.String, types.AnyCollatedString})
  intCastTypes = annotateCast(types.Int, []*types.T{types.Unknown, types.Bool, types.Int, types.Float, types.Decimal, types.String, types.AnyCollatedString,
- types.Timestamp, types.TimestampTZ, types.Date, types.Interval, types.Oid, types.VarBit})
+ types.Timestamp, types.TimestampTZ, types.Date, types.Interval, types.Oid, types.VarBit, types.Jsonb})
  floatCastTypes = annotateCast(types.Float, []*types.T{types.Unknown, types.Bool, types.Int, types.Float, types.Decimal, types.String, types.AnyCollatedString,
- types.Timestamp, types.TimestampTZ, types.Date, types.Interval})
+ types.Timestamp, types.TimestampTZ, types.Date, types.Interval, types.Jsonb})
  decimalCastTypes = annotateCast(types.Decimal, []*types.T{types.Unknown, types.Bool, types.Int, types.Float, types.Decimal, types.String, types.AnyCollatedString,
- types.Timestamp, types.TimestampTZ, types.Date, types.Interval})
+ types.Timestamp, types.TimestampTZ, types.Date, types.Interval, types.Jsonb})
  stringCastTypes = annotateCast(types.String, []*types.T{types.Unknown, types.Bool, types.Int, types.Float, types.Decimal, types.String, types.AnyCollatedString,
  types.VarBit,
  types.AnyArray, types.AnyTuple,

pkg/sql/sem/tree/testdata/eval/cast

@@ -977,3 +977,58 @@ eval
 ARRAY['hello','world']::char(2)[]
 ----
 ARRAY['he','wo']
+
+eval
+'1'::jsonb::int
+----
+1
+
+eval
+'1'::jsonb::float
+----
+1.0
+
+eval
+'1'::jsonb::decimal
+----
+1
+
+eval
+'1'::jsonb::string
+----
+'1'
+
+eval
+'2.0'::jsonb::int
+----
+2
+
+eval
+'2.0'::jsonb::float
+----
+2.0
+
+eval
+'2.0'::jsonb::decimal
+----
+2.0
+
+eval
+'2.0'::jsonb::string
+----
+'2.0'
+
+eval
+'3.14'::jsonb::float
+----
+3.14
+
+eval
+'3.14'::jsonb::decimal
+----
+3.14
+
+eval
+'3.14'::jsonb::string
+----
+'3.14'

pkg/util/json/json.go

@@ -972,6 +972,19 @@ func FromFloat64(v float64) (JSON, error) {
  return jsonNumber(dec), nil
 }
 
+// ToDecimal returns a apd.Decimal given a JSON value
+func ToDecimal(j JSON) (apd.Decimal, error) {
+ j, err := decodeIfNeeded(j)
+ if err != nil {
+ return apd.Decimal{}, err
+ }
+ num, ok := j.(jsonNumber)
+ if !ok {
+ return apd.Decimal{}, errors.AssertionFailedf("cannot convert JSON of type %T to decimal", j)
+ }
+ return apd.Decimal(num), nil
+}
+
 // MakeJSON returns a JSON value given a Go-style representation of JSON.
 // * JSON null is Go `nil`,
 // * JSON true is Go `true`,

pkg/util/json/json_test.go

@@ -2016,3 +2016,65 @@ func TestJSONRemovePath(t *testing.T) {
  }
  }
 }
+
+func TestToDecimal(t *testing.T) {
+ numericCases := []string{
+ "1",
+ "1.0",
+ "3.14",
+ "-3.14",
+ "1.000",
+ "-0.0",
+ "-0.09",
+ "0.08",
+ }
+
+ nonNumericCases := []struct {
+ input string
+ errMsg string
+ }{
+ {"\"1\"", "cannot convert JSON of type json.jsonString to decimal"},
+ {"{}", "cannot convert JSON of type json.jsonObject to decimal"},
+ {"[]", "cannot convert JSON of type json.jsonArray to decimal"},
+ {"true", "cannot convert JSON of type json.jsonTrue to decimal"},
+ {"false", "cannot convert JSON of type json.jsonFalse to decimal"},
+ {"null", "cannot convert JSON of type json.jsonNull to decimal"},
+ }
+
+ for _, tc := range numericCases {
+ t.Run(fmt.Sprintf("numeric - %s", tc), func(t *testing.T) {
+ dec1, _, err := apd.NewFromString(tc)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ json, err := ParseJSON(tc)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ dec2, err := ToDecimal(json)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ if dec1.Cmp(&dec2) != 0 {
+ t.Fatalf("expected %s == %s", dec1.String(), dec2.String())
+ }
+ })
+ }
+
+ for _, tc := range nonNumericCases {
+ t.Run(fmt.Sprintf("nonNumeric - %s", tc), func(t *testing.T) {
+ json, err := ParseJSON(tc.input)
+ if err != nil {
+ t.Fatalf("expected no error")
+ }
+
+ _, err = ToDecimal(json)
+ if err.Error() != tc.errMsg {
+ t.Fatalf("expected %s, got %s", tc.errMsg, err.Error())
+ }
+ })
+ }
+}