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// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package bigquery
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import (
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"errors"
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"fmt"
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"reflect"
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"cloud.google.com/go/internal/atomiccache"
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bq "google.golang.org/api/bigquery/v2"
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)
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// Schema describes the fields in a table or query result.
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type Schema []*FieldSchema
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type FieldSchema struct {
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// The field name.
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// Must contain only letters (a-z, A-Z), numbers (0-9), or underscores (_),
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// and must start with a letter or underscore.
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// The maximum length is 128 characters.
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Name string
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// A description of the field. The maximum length is 16,384 characters.
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Description string
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// Whether the field may contain multiple values.
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Repeated bool
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// Whether the field is required. Ignored if Repeated is true.
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Required bool
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// The field data type. If Type is Record, then this field contains a nested schema,
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// which is described by Schema.
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Type FieldType
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// Describes the nested schema if Type is set to Record.
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Schema Schema
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}
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func (fs *FieldSchema) toBQ() *bq.TableFieldSchema {
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tfs := &bq.TableFieldSchema{
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Description: fs.Description,
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Name: fs.Name,
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Type: string(fs.Type),
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}
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if fs.Repeated {
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tfs.Mode = "REPEATED"
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} else if fs.Required {
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tfs.Mode = "REQUIRED"
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} // else leave as default, which is interpreted as NULLABLE.
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for _, f := range fs.Schema {
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tfs.Fields = append(tfs.Fields, f.toBQ())
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}
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return tfs
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}
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func (s Schema) toBQ() *bq.TableSchema {
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var fields []*bq.TableFieldSchema
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for _, f := range s {
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fields = append(fields, f.toBQ())
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}
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return &bq.TableSchema{Fields: fields}
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}
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func bqToFieldSchema(tfs *bq.TableFieldSchema) *FieldSchema {
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fs := &FieldSchema{
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Description: tfs.Description,
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Name: tfs.Name,
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Repeated: tfs.Mode == "REPEATED",
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Required: tfs.Mode == "REQUIRED",
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Type: FieldType(tfs.Type),
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}
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for _, f := range tfs.Fields {
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fs.Schema = append(fs.Schema, bqToFieldSchema(f))
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}
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return fs
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}
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func bqToSchema(ts *bq.TableSchema) Schema {
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if ts == nil {
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return nil
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}
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var s Schema
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for _, f := range ts.Fields {
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s = append(s, bqToFieldSchema(f))
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}
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return s
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}
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type FieldType string
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const (
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StringFieldType FieldType = "STRING"
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BytesFieldType FieldType = "BYTES"
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IntegerFieldType FieldType = "INTEGER"
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FloatFieldType FieldType = "FLOAT"
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BooleanFieldType FieldType = "BOOLEAN"
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TimestampFieldType FieldType = "TIMESTAMP"
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RecordFieldType FieldType = "RECORD"
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DateFieldType FieldType = "DATE"
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TimeFieldType FieldType = "TIME"
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DateTimeFieldType FieldType = "DATETIME"
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)
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var (
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errNoStruct = errors.New("bigquery: can only infer schema from struct or pointer to struct")
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errUnsupportedFieldType = errors.New("bigquery: unsupported type of field in struct")
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errInvalidFieldName = errors.New("bigquery: invalid name of field in struct")
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errBadNullable = errors.New(`bigquery: use "nullable" only for []byte and struct pointers; for all other types, use a NullXXX type`)
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)
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var typeOfByteSlice = reflect.TypeOf([]byte{})
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// InferSchema tries to derive a BigQuery schema from the supplied struct value.
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// Each exported struct field is mapped to a field in the schema.
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//
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// The following BigQuery types are inferred from the corresponding Go types.
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// (This is the same mapping as that used for RowIterator.Next.) Fields inferred
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// from these types are marked required (non-nullable).
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//
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// STRING string
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// BOOL bool
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// INTEGER int, int8, int16, int32, int64, uint8, uint16, uint32
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// FLOAT float32, float64
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// BYTES []byte
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// TIMESTAMP time.Time
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// DATE civil.Date
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// TIME civil.Time
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// DATETIME civil.DateTime
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//
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// A Go slice or array type is inferred to be a BigQuery repeated field of the
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// element type. The element type must be one of the above listed types.
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//
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// Nullable fields are inferred from the NullXXX types, declared in this package:
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//
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// STRING NullString
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// BOOL NullBool
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// INTEGER NullInt64
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// FLOAT NullFloat64
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// TIMESTAMP NullTimestamp
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// DATE NullDate
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// TIME NullTime
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// DATETIME NullDateTime
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// For a nullable BYTES field, use the type []byte and tag the field "nullable" (see below).
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//
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// A struct field that is of struct type is inferred to be a required field of type
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// RECORD with a schema inferred recursively. For backwards compatibility, a field of
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// type pointer to struct is also inferred to be required. To get a nullable RECORD
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// field, use the "nullable" tag (see below).
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//
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// InferSchema returns an error if any of the examined fields is of type uint,
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// uint64, uintptr, map, interface, complex64, complex128, func, or chan. Future
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// versions may handle these cases without error.
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//
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// Recursively defined structs are also disallowed.
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//
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// Struct fields may be tagged in a way similar to the encoding/json package.
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// A tag of the form
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// bigquery:"name"
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// uses "name" instead of the struct field name as the BigQuery field name.
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// A tag of the form
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// bigquery:"-"
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// omits the field from the inferred schema.
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// The "nullable" option marks the field as nullable (not required). It is only
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// needed for []byte and pointer-to-struct fields, and cannot appear on other
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// fields. In this example, the Go name of the field is retained:
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// bigquery:",nullable"
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func InferSchema(st interface{}) (Schema, error) {
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return inferSchemaReflectCached(reflect.TypeOf(st))
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}
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// TODO(jba): replace with sync.Map for Go 1.9.
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var schemaCache atomiccache.Cache
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type cacheVal struct {
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schema Schema
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err error
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}
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func inferSchemaReflectCached(t reflect.Type) (Schema, error) {
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cv := schemaCache.Get(t, func() interface{} {
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s, err := inferSchemaReflect(t)
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return cacheVal{s, err}
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}).(cacheVal)
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return cv.schema, cv.err
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}
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func inferSchemaReflect(t reflect.Type) (Schema, error) {
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rec, err := hasRecursiveType(t, nil)
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if err != nil {
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return nil, err
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}
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if rec {
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return nil, fmt.Errorf("bigquery: schema inference for recursive type %s", t)
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}
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return inferStruct(t)
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}
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func inferStruct(t reflect.Type) (Schema, error) {
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switch t.Kind() {
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case reflect.Ptr:
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if t.Elem().Kind() != reflect.Struct {
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return nil, errNoStruct
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}
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t = t.Elem()
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fallthrough
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case reflect.Struct:
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return inferFields(t)
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default:
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return nil, errNoStruct
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}
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}
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// inferFieldSchema infers the FieldSchema for a Go type
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func inferFieldSchema(rt reflect.Type, nullable bool) (*FieldSchema, error) {
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// Only []byte and struct pointers can be tagged nullable.
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if nullable && !(rt == typeOfByteSlice || rt.Kind() == reflect.Ptr && rt.Elem().Kind() == reflect.Struct) {
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return nil, errBadNullable
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}
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switch rt {
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case typeOfByteSlice:
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return &FieldSchema{Required: !nullable, Type: BytesFieldType}, nil
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case typeOfGoTime:
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return &FieldSchema{Required: true, Type: TimestampFieldType}, nil
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case typeOfDate:
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return &FieldSchema{Required: true, Type: DateFieldType}, nil
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case typeOfTime:
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return &FieldSchema{Required: true, Type: TimeFieldType}, nil
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case typeOfDateTime:
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return &FieldSchema{Required: true, Type: DateTimeFieldType}, nil
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}
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if ft := nullableFieldType(rt); ft != "" {
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return &FieldSchema{Required: false, Type: ft}, nil
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}
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if isSupportedIntType(rt) || isSupportedUintType(rt) {
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return &FieldSchema{Required: true, Type: IntegerFieldType}, nil
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}
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switch rt.Kind() {
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case reflect.Slice, reflect.Array:
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et := rt.Elem()
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if et != typeOfByteSlice && (et.Kind() == reflect.Slice || et.Kind() == reflect.Array) {
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// Multi dimensional slices/arrays are not supported by BigQuery
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return nil, errUnsupportedFieldType
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}
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if nullableFieldType(et) != "" {
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// Repeated nullable types are not supported by BigQuery.
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return nil, errUnsupportedFieldType
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}
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f, err := inferFieldSchema(et, false)
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if err != nil {
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return nil, err
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}
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f.Repeated = true
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f.Required = false
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return f, nil
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case reflect.Ptr:
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if rt.Elem().Kind() != reflect.Struct {
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return nil, errUnsupportedFieldType
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}
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fallthrough
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case reflect.Struct:
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nested, err := inferStruct(rt)
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if err != nil {
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return nil, err
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}
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return &FieldSchema{Required: !nullable, Type: RecordFieldType, Schema: nested}, nil
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case reflect.String:
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return &FieldSchema{Required: !nullable, Type: StringFieldType}, nil
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case reflect.Bool:
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return &FieldSchema{Required: !nullable, Type: BooleanFieldType}, nil
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case reflect.Float32, reflect.Float64:
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return &FieldSchema{Required: !nullable, Type: FloatFieldType}, nil
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default:
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return nil, errUnsupportedFieldType
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}
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}
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// inferFields extracts all exported field types from struct type.
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func inferFields(rt reflect.Type) (Schema, error) {
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var s Schema
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fields, err := fieldCache.Fields(rt)
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if err != nil {
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return nil, err
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}
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for _, field := range fields {
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var nullable bool
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for _, opt := range field.ParsedTag.([]string) {
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if opt == nullableTagOption {
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nullable = true
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break
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}
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}
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f, err := inferFieldSchema(field.Type, nullable)
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if err != nil {
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return nil, err
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}
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f.Name = field.Name
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s = append(s, f)
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}
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return s, nil
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}
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// isSupportedIntType reports whether t is an int type that can be properly
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// represented by the BigQuery INTEGER/INT64 type.
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func isSupportedIntType(t reflect.Type) bool {
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switch t.Kind() {
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case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
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return true
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default:
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return false
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}
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}
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// isSupportedIntType reports whether t is a uint type that can be properly
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// represented by the BigQuery INTEGER/INT64 type.
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func isSupportedUintType(t reflect.Type) bool {
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switch t.Kind() {
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case reflect.Uint8, reflect.Uint16, reflect.Uint32:
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return true
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default:
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return false
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}
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}
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// typeList is a linked list of reflect.Types.
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type typeList struct {
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t reflect.Type
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next *typeList
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}
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func (l *typeList) has(t reflect.Type) bool {
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for l != nil {
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if l.t == t {
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return true
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}
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l = l.next
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}
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return false
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}
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// hasRecursiveType reports whether t or any type inside t refers to itself, directly or indirectly,
|
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// via exported fields. (Schema inference ignores unexported fields.)
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func hasRecursiveType(t reflect.Type, seen *typeList) (bool, error) {
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for t.Kind() == reflect.Ptr || t.Kind() == reflect.Slice || t.Kind() == reflect.Array {
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t = t.Elem()
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}
|
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if t.Kind() != reflect.Struct {
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return false, nil
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}
|
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if seen.has(t) {
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return true, nil
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}
|
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fields, err := fieldCache.Fields(t)
|
||||
if err != nil {
|
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return false, err
|
||||
}
|
||||
seen = &typeList{t, seen}
|
||||
// Because seen is a linked list, additions to it from one field's
|
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// recursive call will not affect the value for subsequent fields' calls.
|
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for _, field := range fields {
|
||||
ok, err := hasRecursiveType(field.Type, seen)
|
||||
if err != nil {
|
||||
return false, err
|
||||
}
|
||||
if ok {
|
||||
return true, nil
|
||||
}
|
||||
}
|
||||
return false, nil
|
||||
}
|
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Reference in New Issue
Block a user