[
https://issues.apache.org/jira/browse/BEAM-9615?focusedWorklogId=467440&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-467440
]
ASF GitHub Bot logged work on BEAM-9615:
----------------------------------------
Author: ASF GitHub Bot
Created on: 06/Aug/20 17:28
Start Date: 06/Aug/20 17:28
Worklog Time Spent: 10m
Work Description: lostluck commented on a change in pull request #12471:
URL: https://github.com/apache/beam/pull/12471#discussion_r466572347
##########
File path: sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go
##########
@@ -0,0 +1,245 @@
+// Licensed to the Apache Software Foundation (ASF) under one or more
+// contributor license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright ownership.
+// The ASF licenses this file to You 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 schema contains utility functions for relating Go types and Beam
Schemas.
+//
+// Not all Go types can be converted to schemas. This is Go is more expressive
than
+// Beam schemas. Just as not all Go types can be serialized, similarly,
+// not all Beam Schemas will have a conversion to Go types, until the correct
+// mechanism exists in the SDK to handle them.
+//
+// While efforts will be made to have conversions be reversable, this will not
+// be possible in all instances. Eg. Go arrays as fields will be converted to
+// Beam Arrays, but a Beam Array type will map by default to a Go slice.
+package schema
+
+import (
+ "fmt"
+ "reflect"
+ "strings"
+
+ "github.com/apache/beam/sdks/go/pkg/beam/core/util/reflectx"
+ "github.com/apache/beam/sdks/go/pkg/beam/internal/errors"
+ pipepb "github.com/apache/beam/sdks/go/pkg/beam/model/pipeline_v1"
+)
+
+// FromType returns a Beam Schema of the passed in type.
+// Returns an error if the type cannot be converted to a Schema.
+func FromType(ot reflect.Type) (*pipepb.Schema, error) {
+ t := ot // keep the original type for errors.
+ // The top level schema for a pointer to struct and the struct is the
same.
+ if t.Kind() == reflect.Ptr {
+ t = t.Elem()
+ }
+ if t.Kind() != reflect.Struct {
+ return nil, errors.Errorf("cannot convert %v to schema.
FromType only converts structs to schemas", ot)
+ }
+ return structToSchema(t), nil
+}
+
+func structToSchema(t reflect.Type) *pipepb.Schema {
+ fields := make([]*pipepb.Field, 0, t.NumField())
+ for i := 0; i < t.NumField(); i++ {
+ fields = append(fields, structFieldToField(t.Field(i)))
+ }
+ return &pipepb.Schema{
+ Fields: fields,
+ }
+}
+
+func structFieldToField(sf reflect.StructField) *pipepb.Field {
+ name := sf.Name
+ if tag := sf.Tag.Get("beam"); tag != "" {
+ name, _ = parseTag(tag)
+ }
+ ftype := reflectTypeToFieldType(sf.Type)
+
+ return &pipepb.Field{
+ Name: name,
+ Type: ftype,
+ }
+}
+
+func reflectTypeToFieldType(ot reflect.Type) *pipepb.FieldType {
+ var isPtr bool
+ t := ot
+ if t.Kind() == reflect.Ptr {
+ isPtr = true
+ t = t.Elem()
+ }
+ switch t.Kind() {
+ case reflect.Map:
+ kt := reflectTypeToFieldType(t.Key())
+ vt := reflectTypeToFieldType(t.Elem())
+ return &pipepb.FieldType{
+ Nullable: isPtr,
+ TypeInfo: &pipepb.FieldType_MapType{
+ MapType: &pipepb.MapType{
+ KeyType: kt,
+ ValueType: vt,
+ },
+ },
+ }
+ case reflect.Struct:
+ sch := structToSchema(t)
+ return &pipepb.FieldType{
+ Nullable: isPtr,
+ TypeInfo: &pipepb.FieldType_RowType{
+ RowType: &pipepb.RowType{
+ Schema: sch,
+ },
+ },
+ }
+ case reflect.Slice, reflect.Array:
+ // Special handling for []byte
+ if t == reflectx.ByteSlice {
+ return &pipepb.FieldType{
+ Nullable: isPtr,
+ TypeInfo: &pipepb.FieldType_AtomicType{
+ AtomicType: pipepb.AtomicType_BYTES,
+ },
+ }
+ }
+ vt := reflectTypeToFieldType(t.Elem())
+ return &pipepb.FieldType{
+ Nullable: isPtr,
+ TypeInfo: &pipepb.FieldType_ArrayType{
+ ArrayType: &pipepb.ArrayType{
+ ElementType: vt,
+ },
+ },
+ }
+ case reflect.Interface, reflect.Chan, reflect.UnsafePointer,
reflect.Complex128, reflect.Complex64, reflect.Int:
+ panic(fmt.Sprintf("Unsupported type to convert to schema: %v",
ot))
Review comment:
Good catch. I was definitely doing this out of iteration laziness.
Handling error propagation now.
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Issue Time Tracking
-------------------
Worklog Id: (was: 467440)
Time Spent: 10h 20m (was: 10h 10m)
> [Go SDK] Beam Schemas
> ---------------------
>
> Key: BEAM-9615
> URL: https://issues.apache.org/jira/browse/BEAM-9615
> Project: Beam
> Issue Type: New Feature
> Components: sdk-go
> Reporter: Robert Burke
> Assignee: Robert Burke
> Priority: P2
> Time Spent: 10h 20m
> Remaining Estimate: 0h
>
> Schema support is required for advanced cross language features in Beam, and
> has the opportunity to replace the current default JSON encoding of elements.
> Some quick notes, though a better fleshed out doc with details will be
> forthcoming:
> * All base coders should be implemented, and listed as coder capabilities. I
> think only stringutf8 is missing presently.
> * Should support fairly arbitrary user types, seamlessly. That is, users
> should be able to rely on it "just working" if their type is compatible.
> * Should support schema metadata tagging.
> In particular, one breaking shift in the default will be to explicitly fail
> pipelines if elements have unexported fields, when no other custom coder has
> been added. This has been a source of errors/dropped data/keys and a simply
> warning at construction time won't cut it. However, we could provide a manual
> "use beam schemas, but ignore unexported fields" registration as a work
> around.
> Edit: Doc is now at https://s.apache.org/beam-go-schemas
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