Fixing bugs for building a prefix index with existing table data

go/libraries/doltcore/migrate/tuples.go

@@ -331,7 +331,7 @@ func translateBlobField(ctx context.Context, ns tree.NodeStore, value types.Blob
 	case val.StringAddrEnc, val.BytesAddrEnc:
 		// common case
 	default:
-		return fmt.Errorf("unexpecte encoding for blob (%d)", b.Desc.Types[idx].Enc)
+		return fmt.Errorf("unexpected encoding for blob (%d)", b.Desc.Types[idx].Enc)
 	}
 
 	buf := make([]byte, value.Len())

go/libraries/doltcore/sqle/index/key_builder.go

@@ -31,6 +31,7 @@ func NewSecondaryKeyBuilder(sch schema.Schema, def schema.Index, idxDesc val.Tup
 	b.pool = p
 	b.nodeStore = nodeStore
 	b.sch = sch
+	b.def = def
 
 	keyless := schema.IsKeyless(sch)
 	if keyless {
@@ -64,6 +65,8 @@ func NewSecondaryKeyBuilder(sch schema.Schema, def schema.Index, idxDesc val.Tup
 type SecondaryKeyBuilder struct {
 	// sch holds the schema of the table on which the secondary index is created
 	sch schema.Schema
+	// def holds the definition of the secondary index
+	def schema.Index
 	// mapping defines how to map fields from the source table's schema to this index's tuple layout
 	mapping val.OrdinalMapping
 	// split marks the index in the secondary index's key tuple that splits the main table's
@@ -96,6 +99,10 @@ func (b SecondaryKeyBuilder) SecondaryKeyFromRow(ctx context.Context, k, v val.T
 				return nil, err
 			}
 
+			if len(b.def.PrefixLengths()) > to {
+				value = val.TrimValueToPrefixLength(value, b.def.PrefixLengths()[to])
+			}
+
 			err = PutField(ctx, b.nodeStore, b.builder, to, value)
 			if err != nil {
 				return nil, err

go/libraries/doltcore/sqle/writer/prolly_index_writer.go

@@ -290,21 +290,7 @@ func (m prollySecondaryIndexWriter) trimKeyPart(to int, keyPart interface{}) int
 	if len(m.prefixLengths) > to {
 		prefixLength = m.prefixLengths[to]
 	}
-	if prefixLength != 0 {
-		switch kp := keyPart.(type) {
-		case string:
-			if prefixLength > uint16(len(kp)) {
-				prefixLength = uint16(len(kp))
-			}
-			keyPart = kp[:prefixLength]
-		case []uint8:
-			if prefixLength > uint16(len(kp)) {
-				prefixLength = uint16(len(kp))
-			}
-			keyPart = kp[:prefixLength]
-		}
-	}
-	return keyPart
+	return val.TrimValueToPrefixLength(keyPart, prefixLength)
 }
 
 func (m prollySecondaryIndexWriter) keyFromRow(ctx context.Context, sqlRow sql.Row) (val.Tuple, error) {

go/store/val/prefix.go

@@ -0,0 +1,39 @@
+// Copyright 2023 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package val
+
+// TrimValueToPrefixLength trims |value| to |prefixLength| if it is longer
+// and if it is either a []byte or string type. If |prefixLength| is zero,
+// then |value| will be returned without being trimmed.
+func TrimValueToPrefixLength(value interface{}, prefixLength uint16) interface{} {
+	if prefixLength == 0 {
+		return value
+	}
+
+	switch v := value.(type) {
+	case string:
+		if prefixLength > uint16(len(v)) {
+			prefixLength = uint16(len(v))
+		}
+		value = v[:prefixLength]
+	case []uint8:
+		if prefixLength > uint16(len(v)) {
+			prefixLength = uint16(len(v))
+		}
+		value = v[:prefixLength]
+	}
+
+	return value
+}