fix: Remove various panic's

Author: devanbenz

storage/reads/array_cursor.gen.go.tmpl

@@ -27,7 +27,7 @@ func newLimitArrayCursor(cur cursors.Cursor) (cursors.Cursor, error) {
 	default:
 		return nil, &errors2.Error{
 			Code: errors2.EInvalid,
-			Msg: fmt.Sprintf("unreachable: %s", arrayCursorType(cur)),
+			Msg: fmt.Sprintf("unsupported limit array cursor type: %s", arrayCursorType(cur)),
 		}
 	}
 }
@@ -44,7 +44,7 @@ func newWindowFirstArrayCursor(cur cursors.Cursor, window interval.Window) (curs
 	default:
 		return nil, &errors2.Error{
 			Code: errors2.EInvalid,
-			Msg: fmt.Sprintf("unreachable: %s", arrayCursorType(cur)),
+			Msg: fmt.Sprintf("unsupported window first cursor type: %s", arrayCursorType(cur)),
 		}
 	}
 }
@@ -61,7 +61,7 @@ func newWindowLastArrayCursor(cur cursors.Cursor, window interval.Window) (curso
 	default:
 		return nil, &errors2.Error{
 			Code: errors2.EInvalid,
-			Msg: fmt.Sprintf("unreachable: %s", arrayCursorType(cur)),
+			Msg: fmt.Sprintf("unsupported window last cursor type: %s", arrayCursorType(cur)),
 		}
 	}
 }
@@ -75,7 +75,7 @@ func newWindowCountArrayCursor(cur cursors.Cursor, window interval.Window) (curs
 	default:
 		return nil, &errors2.Error{
 			Code: errors2.EInvalid,
-			Msg: fmt.Sprintf("unreachable: %s", arrayCursorType(cur)),
+			Msg: fmt.Sprintf("unsupported window count cursor type: %s", arrayCursorType(cur)),
 		}
 	}
 }

storage/reads/array_cursor.go

@@ -3,6 +3,7 @@ package reads
 import (
 	"context"
 	"fmt"
+	errors2 "github.com/influxdata/influxdb/v2/kit/platform/errors"
 
 	"github.com/influxdata/flux/interval"
 	"github.com/influxdata/influxdb/v2/storage/reads/datatypes"
@@ -46,8 +47,10 @@ func newWindowAggregateArrayCursor(ctx context.Context, agg *datatypes.Aggregate
 	case datatypes.Aggregate_AggregateTypeMean:
 		return newWindowMeanArrayCursor(cursor, window)
 	default:
-		// TODO(sgc): should be validated higher up
-		panic("invalid aggregate")
+		return nil, &errors2.Error{
+			Code: errors2.EInvalid,
+			Msg:  fmt.Sprintf("unsupported window aggregate cursor: %s", agg.Type),
+		}
 	}
 }
 
@@ -101,7 +104,7 @@ func newMultiShardArrayCursors(ctx context.Context, start, end int64, asc bool)
 	return m
 }
 
-func (m *multiShardArrayCursors) createCursor(row SeriesRow) cursors.Cursor {
+func (m *multiShardArrayCursors) createCursor(row SeriesRow) (cursors.Cursor, error) {
 	m.req.Name = row.Name
 	m.req.Tags = row.SeriesTags
 	m.req.Field = row.Field
@@ -120,26 +123,29 @@ func (m *multiShardArrayCursors) createCursor(row SeriesRow) cursors.Cursor {
 	}
 
 	if cur == nil || err != nil {
-		return nil
+		return nil, nil
 	}
 
 	switch c := cur.(type) {
 	case cursors.IntegerArrayCursor:
 		m.cursors.i.reset(c, row.Query, cond)
-		return &m.cursors.i
+		return &m.cursors.i, nil
 	case cursors.FloatArrayCursor:
 		m.cursors.f.reset(c, row.Query, cond)
-		return &m.cursors.f
+		return &m.cursors.f, nil
 	case cursors.UnsignedArrayCursor:
 		m.cursors.u.reset(c, row.Query, cond)
-		return &m.cursors.u
+		return &m.cursors.u, nil
 	case cursors.StringArrayCursor:
 		m.cursors.s.reset(c, row.Query, cond)
-		return &m.cursors.s
+		return &m.cursors.s, nil
 	case cursors.BooleanArrayCursor:
 		m.cursors.b.reset(c, row.Query, cond)
-		return &m.cursors.b
+		return &m.cursors.b, nil
 	default:
-		panic(fmt.Sprintf("unreachable: %T", cur))
+		return nil, &errors2.Error{
+			Code: errors2.EInvalid,
+			Msg:  fmt.Sprintf("unsupported cursor type while creating cursor: %s", arrayCursorType(cur)),
+		}
 	}
 }