spanvalue

package module
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 Go to latest Published: Apr 5, 2026 License: MIT Imports: 15 Imported by: 1

README

spanvalue

Go Reference

Helpers for working with Cloud Spanner’s spanner.GenericColumnValue and related client types: format values to text (literals, JSON, CLI-style output) and construct values from Go types.

Package Role
github.com/apstndb/spanvalue Format spanner.GenericColumnValue and *spanner.Row using FormatConfig and presets such as LiteralFormatConfig, JSONFormatConfig, SpannerCLICompatibleFormatConfig.
github.com/apstndb/spanvalue/gcvctor Build spanner.GenericColumnValue (scalars, ARRAY, STRUCT, typed nulls). Types are often composed with github.com/apstndb/spantype/typector.

Documentation

Overview

Package spanvalue formats Cloud Spanner data from the Go client (cloud.google.com/go/spanner): cloud.google.com/go/spanner.GenericColumnValue values for individual columns and `*spanner.Row` values for full rows (cloud.google.com/go/spanner.Row), into strings for SQL literals, JSON, Spanner CLI–compatible text, and related styles.

Configure output with FormatConfig. Use the constructors LiteralFormatConfig, SimpleFormatConfig, SpannerCLICompatibleFormatConfig, and JSONFormatConfig to pick a preset. FormatConfig.FormatColumn runs FormatComplexFunc plugins first, then built-in ARRAY, STRUCT, and scalar formatting. Convenience entry points include FormatRowLiteral, FormatColumnLiteral, FormatRowJSONObject, and FormatRowSpannerCLICompatible.

To build cloud.google.com/go/spanner.GenericColumnValue values from Go types, see the sibling package github.com/apstndb/spanvalue/gcvctor.

Index

Constants

This section is empty.

Variables

View Source 
var (
	ErrUnknownType      = errors.New("unknown type")
	ErrMismatchedFields = errors.New("mismatched struct value/field count")
)
View Source 
var ErrFallthrough = errors.New("fallthrough")
View Source 
var FormatJSONObjectStruct = NewJSONObjectStructFormatter(nil)

FormatJSONObjectStruct formats struct fields as a JSON object with nil namer. Unnamed struct fields produce empty-string keys, matching Spanner's own representation.

View Source 
var FormatTypedStruct = FormatStruct{
	FormatStructParen: formatTypedStructParen,
	FormatStructField: formatSimpleStructField,
}

Functions

func ColumnNames added in v0.1.10 

func ColumnNames(fields []*sppb.StructType_Field, namer UnnamedFieldNamer) ([]string, error)

ColumnNames returns the names of the provided fields. Unnamed fields are kept as empty strings unless a non-nil namer is provided, in which case the namer is used to generate names for unnamed fields. If a non-nil UnnamedFieldNamer returns an empty string or repeatedly returns colliding names such that a unique column name cannot be chosen, ColumnNames returns a non-nil error describing the contract violation.

func FormatBracketStruct 

func FormatBracketStruct(typ *sppb.Type, toplevel bool, fieldStrings []string) (string, error)

func FormatColumnLiteral 

func FormatColumnLiteral(value spanner.GenericColumnValue) (string, error)

func FormatColumnSpannerCLICompatible 

func FormatColumnSpannerCLICompatible(value spanner.GenericColumnValue) (string, error)

func FormatCompactArray added in v0.1.9 

func FormatCompactArray(_ *sppb.Type, _ bool, elemStrings []string) (string, error)

FormatCompactArray formats array elements without spaces between separators. Output: [elem1,elem2,elem3]

func FormatEnumAsCast 

func FormatEnumAsCast(formatter Formatter, value spanner.GenericColumnValue, toplevel bool) (string, error)

func FormatJSONSimpleValue added in v0.1.9 

func FormatJSONSimpleValue(formatter Formatter, value spanner.GenericColumnValue, _ bool) (string, error)

FormatJSONSimpleValue is a FormatComplexFunc that formats non-ARRAY, non-STRUCT types as valid JSON values. It returns ErrFallthrough for ARRAY and STRUCT so that the built-in handlers format them.

For most types, structpb.Value.MarshalJSON() produces the correct JSON representation (BOOL→true/false, FLOAT→number, STRING→"quoted", NULL→null, NaN/Inf→"NaN"/"Infinity"). Only INT64, ENUM, and JSON columns need special handling:

  • INT64: Spanner encodes as StringValue("42"), MarshalJSON() would produce "42" (quoted), but we want 42 (unquoted number).
  • ENUM: Spanner stores proto enum values as INT64; same handling as INT64.
  • JSON: Spanner encodes as StringValue('{"key":"value"}'), MarshalJSON() would produce escaped quoted string, but we want the raw JSON value passed through.

func FormatNullableSpannerCLICompatible 

func FormatNullableSpannerCLICompatible(value NullableValue) (string, error)

func FormatOptionallyTypedArray 

func FormatOptionallyTypedArray(typ *sppb.Type, toplevel bool, elemStrings []string) (string, error)

func FormatProtoAsCast 

func FormatProtoAsCast(formatter Formatter, value spanner.GenericColumnValue, toplevel bool) (string, error)

func FormatRowColumns added in v0.1.10 

func FormatRowColumns(fc *FormatConfig, columnNames []string, values []spanner.GenericColumnValue) ([]string, error)

FormatRowColumns formats a row represented as column names plus GCV values. The column names are validated for shape compatibility, but the formatted cell values come from the GCVs themselves.

func FormatRowJSONObject added in v0.1.9 

func FormatRowJSONObject(fc *FormatConfig, row *spanner.Row, namer UnnamedFieldNamer) (string, error)

FormatRowJSONObject formats a spanner.Row as a single JSON object string using the given FormatConfig for value formatting and column names as keys. The FormatConfig must produce standalone JSON values per column (e.g., JSONFormatConfig()). Using a non-JSON config produces syntactically invalid output. Empty column names (e.g., from expressions without aliases like SELECT 1+1) are assigned names by the provided namer function. If namer is nil, empty names are kept as empty-string JSON keys. Returns an error if the namer returns an empty name, or if repeated name collisions prevent choosing a unique name for a field. Output: {"col1":val1,"col2":val2,...}

func FormatRowJSONObjectFromColumns added in v0.1.10 

func FormatRowJSONObjectFromColumns(fc *FormatConfig, columnNames []string, values []spanner.GenericColumnValue, namer UnnamedFieldNamer) (string, error)

FormatRowJSONObjectFromColumns formats a row represented as column names plus GCV values into a JSON object string. The provided FormatConfig must emit standalone JSON values per column (for example, as configured by JSONFormatConfig()), otherwise the assembled object may be syntactically invalid JSON.

func FormatRowLiteral 

func FormatRowLiteral(value *spanner.Row) ([]string, error)

func FormatRowSpannerCLICompatible 

func FormatRowSpannerCLICompatible(row *spanner.Row) ([]string, error)

func FormatSimpleStructField 

func FormatSimpleStructField(fc *FormatConfig, field *sppb.StructType_Field, value *structpb.Value) (string, error)

func FormatTupleStruct 

func FormatTupleStruct(typ *sppb.Type, toplevel bool, fieldStrings []string) (string, error)

func FormatTypelessStructField 

func FormatTypelessStructField(fc *FormatConfig, field *sppb.StructType_Field, value *structpb.Value) (string, error)

func FormatUntypedArray 

func FormatUntypedArray(_ *sppb.Type, _ bool, elemStrings []string) (string, error)

func IndexedUnnamedFieldNamer added in v0.1.9 

func IndexedUnnamedFieldNamer(index int) string

IndexedUnnamedFieldNamer produces names like "_0", "_1", etc. The underscore prefix minimizes collision with user-defined names. Suitable for row columns (e.g., SELECT 1+1 produces "_0").

func IsNull added in v0.1.10 

func IsNull(gcv spanner.GenericColumnValue) bool

IsNull reports whether gcv represents a NULL value. A nil gcv.Value is treated as NULL.

Types

type FormatArrayFunc 

type FormatArrayFunc func(typ *sppb.Type, toplevel bool, elemStrings []string) (string, error)

type FormatComplexFunc 

type FormatComplexFunc = func(formatter Formatter, value spanner.GenericColumnValue, toplevel bool) (string, error)

FormatComplexFunc is a function to format spanner.GenericColumnValue. If it returns ErrFallthrough, value will pass through to next step.

type FormatConfig 

type FormatConfig struct {
	NullString           string
	FormatArray          FormatArrayFunc
	FormatStruct         FormatStruct
	FormatComplexPlugins []FormatComplexFunc
	FormatNullable       FormatNullableFunc
}

func JSONFormatConfig added in v0.1.9 

func JSONFormatConfig() *FormatConfig

JSONFormatConfig returns a new FormatConfig that produces valid JSON value strings for each Spanner value. Each call returns a fresh instance that the caller may customize.

Each formatted string is a standalone JSON value:

  • NULL → null
  • BOOL → true / false
  • INT64 → 42 (unquoted number)
  • FLOAT32/FLOAT64 → 3.14 (NaN/Inf as quoted strings)
  • ENUM → 42 (unquoted number, Spanner stores proto enum values as INT64)
  • STRING, BYTES, TIMESTAMP, DATE, NUMERIC, PROTO, INTERVAL, UUID → "quoted string"
  • JSON column → raw JSON value (passed through)
  • ARRAY → [elem1,elem2,...]
  • STRUCT → {"field1":val1,"field2":val2,...}

func LiteralFormatConfig 

func LiteralFormatConfig() *FormatConfig

LiteralFormatConfig returns a new FormatConfig that produces parseable SQL literal expressions with type annotations.

func SimpleFormatConfig 

func SimpleFormatConfig() *FormatConfig

SimpleFormatConfig returns a new FormatConfig that produces human-readable output using client library conventions.

func SpannerCLICompatibleFormatConfig 

func SpannerCLICompatibleFormatConfig() *FormatConfig

SpannerCLICompatibleFormatConfig returns a new FormatConfig that matches the output format of spanner-cli.

func (*FormatConfig) FormatColumn 

func (fc *FormatConfig) FormatColumn(value spanner.GenericColumnValue, toplevel bool) (string, error)

func (*FormatConfig) FormatRow 

func (fc *FormatConfig) FormatRow(row *spanner.Row) ([]string, error)

func (*FormatConfig) FormatToplevelColumn 

func (fc *FormatConfig) FormatToplevelColumn(value spanner.GenericColumnValue) (string, error)

func (*FormatConfig) GetNullString added in v0.1.10 

func (fc *FormatConfig) GetNullString() string

type FormatNullableFunc 

type FormatNullableFunc = func(value NullableValue) (string, error)

type FormatStruct 

type FormatStruct struct {
	FormatStructField FormatStructFieldFunc
	FormatStructParen FormatStructParenFunc
}

type FormatStructFieldFunc 

type FormatStructFieldFunc func(fc *FormatConfig, field *sppb.StructType_Field, value *structpb.Value) (string, error)

type FormatStructParenFunc 

type FormatStructParenFunc func(typ *sppb.Type, toplevel bool, fieldStrings []string) (string, error)

func NewJSONObjectStructFormatter added in v0.1.9 

func NewJSONObjectStructFormatter(namer UnnamedFieldNamer) FormatStructParenFunc

NewJSONObjectStructFormatter creates a FormatStructParenFunc that formats struct fields as a JSON object with field names as keys. Unnamed fields are assigned names by the provided namer function. If namer is nil, unnamed fields keep empty-string keys (which produces duplicate keys — valid per RFC 8259 but may cause issues with parsers that deduplicate keys). Returns an error if the namer returns an empty name, or if repeated name collisions prevent choosing a unique name for a field. Output: {"field1":val1,"field2":val2,...}

type Formatter 

type Formatter interface {
	FormatColumn(value spanner.GenericColumnValue, toplevel bool) (string, error)
	GetNullString() string
}

type NullBytes 

type NullBytes []byte

func (NullBytes) IsNull 

func (n NullBytes) IsNull() bool

func (NullBytes) String 

func (n NullBytes) String() string

type NullableValue 

type NullableValue interface {
	spanner.NullableValue
	fmt.Stringer
}

type UnnamedFieldNamer added in v0.1.9 

type UnnamedFieldNamer func(index int) string

UnnamedFieldNamer generates a name for an unnamed field or column. The index argument is a monotonically increasing counter (not necessarily the field's positional index) that may skip values due to collision avoidance. It must return distinct non-empty names for distinct indices. Functions that accept UnnamedFieldNamer (such as NewJSONObjectStructFormatter and FormatRowJSONObject) return an error if the namer violates this contract. Pass nil instead of a namer to keep unnamed fields as empty-string keys.

Source Files

View all Source files

Directories

Path Synopsis
Package gcvctor constructs cloud.google.com/go/spanner.GenericColumnValue values from Go values and explicit cloud.google.com/go/spanner/apiv1/spannerpb.Type metadata, using github.com/apstndb/spantype/typector for type shapes.
 Package gcvctor constructs cloud.google.com/go/spanner.GenericColumnValue values from Go values and explicit cloud.google.com/go/spanner/apiv1/spannerpb.Type metadata, using github.com/apstndb/spantype/typector for type shapes.

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