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API Reference ​

Constants ​

TableName ​

DynamoDB table name.

go
const TableName = "table-name"

Column ​

Table column names.

go
const ColumnId = "id"
const ColumnEmail = "email"
const ColumnTimestamp = "timestamp"

Column naming convention:

All defined columns start with Column and follow CamelCase syntax.

Index ​

Names of secondary indexes.

go
const IndexEmailIndex = "email-index"

Index naming convention:

All defined indexes start with Index and follow CamelCase syntax.

Attribute ​

Slice of strings with all attribute names from the DynamoDB table.

go
var AttributeNames = []string{"id", "timestamp", "email"}

KeyAttribute ​

Slice of strings containing the primary key attributes of the DynamoDB table.

go
var KeyAttributeNames = []string{"id", "timestamp"}

Data Structs ​

SchemaItem ​

Structure representing a single record in DynamoDB.

go
type SchemaItem struct {
  Id        string `dynamodbav:"id"`
  Email     string `dynamodbav:"email"`
  Timestamp int64  `dynamodbav:"timestamp"`
}

TableSchema ​

Global variable of type DynamoSchema that contains all table metadata.

go
var TableSchema = DynamoSchema{
  TableName: "table-name",
  HashKey:   "id",
  RangeKey:  "timestamp",
  // ...
}
More...
go
var TableSchema = DynamoSchema{
   TableName: "user-profiles",
   HashKey:   "user_id",
   RangeKey:  "profile_type",
   
   Attributes: []Attribute{
       {Name: "user_id", Type: "S"},
       {Name: "profile_type", Type: "S"},
       {Name: "created_at", Type: "N"},
       {Name: "status", Type: "S"},
   },
   
   CommonAttributes: []Attribute{
       {Name: "email", Type: "S"},
       {Name: "is_active", Type: "BOOL"},
       {Name: "tags", Type: "SS"},
       {Name: "scores", Type: "NS"},
   },
   
   SecondaryIndexes: []SecondaryIndex{
       {
           Name:           "status-created-index",
           HashKey:        "status",
           RangeKey:       "created_at",
           ProjectionType: "ALL",
       },
       {
           Name:           "category-profile-index", 
           HashKey:        "category_id",
           RangeKey:       "profile_type",
           ProjectionType: "INCLUDE",
           NonKeyAttributes: []string{"email", "is_active"},
       },
       {
           Name:             "user-created-lsi",
           HashKey:          "user_id",
           RangeKey:         "created_at",
           ProjectionType:   "KEYS_ONLY",
           HashKeyParts: []CompositeKeyPart{
               {IsConstant: false, Value: "user_id"},
               {IsConstant: true, Value: "PROFILE"},
           },
           RangeKeyParts: []CompositeKeyPart{
               {IsConstant: false, Value: "created_at"},
               {IsConstant: true, Value: "2024"},
           },
       },
   },
   
   FieldsMap: map[string]FieldInfo{
       "user_id": {
           DynamoType:       "S",
           IsKey:            true,
           IsHashKey:        true,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("S"),
       },
       "profile_type": {
           DynamoType:       "S",
           IsKey:            true,
           IsHashKey:        false,
           IsRangeKey:       true,
           AllowedOperators: buildAllowedOperators("S"),
       },
       "created_at": {
           DynamoType:       "N",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("N"),
       },
       "status": {
           DynamoType:       "S",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("S"),
       },
       "email": {
           DynamoType:       "S",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("S"),
       },
       "is_active": {
           DynamoType:       "BOOL",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("BOOL"),
       },
       "tags": {
           DynamoType:       "SS",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("SS"),
       },
       "scores": {
           DynamoType:       "NS",
           IsKey:            false,
           IsHashKey:        false,
           IsRangeKey:       false,
           AllowedOperators: buildAllowedOperators("NS"),
       },
   },
}

QueryBuilder ​

With / Filter

  • With (WithEQ, WithGT, etc.)
    Applied BEFORE reading data from DynamoDB and determine which items will be read.

  • Filter (FilterEQ, FilterGT, etc.)
    Applied AFTER reading data and affect only the returned result set.

NewQueryBuilder ​

Create new QueryBuilder object.

go
func NewQueryBuilder() *QueryBuilder

qb.Limit ​

Sets a limit on the number of results.

go
func (qb *QueryBuilder) Limit(limit int) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  Limit(10)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

qb.WithIndex ​

Explicitly specifies which secondary index to use for the query instead of automatic selection.

go
func (qb *QueryBuilder) WithIndex(indexName string) *QueryBuilder

!!! Bug in v0.0.2 version.

method will not generate with min mode.

Example

Multiple indexes schema:

json
{
  "table_name": "user-orders",
  "hash_key": "user_id",
  "range_key": "order_id", 
  "attributes": [
    {"name": "user_id", "type": "S"},
    {"name": "order_id", "type": "S"},
    {"name": "status", "type": "S"}
  ],
  "secondary_indexes": [
    {
      "name": "lsi_by_status",
      "type": "LSI",
      "hash_key": "user_id",
      "range_key": "status"
    },
    {
      "name": "gsi_by_status", 
      "type": "GSI",
      "hash_key": "status"
    }
  ]
}

Query examples:

go
query1 := userorders.NewQueryBuilder().
  WithEQ("user_id", "user123").
  WithEQ("status", "active")

input1, _ := query1.BuildQuery()
fmt.Printf("Auto: %s\n", *input1.IndexName)
// Output: Auto: lsi_by_status

query2 := userorders.NewQueryBuilder().
  WithEQ("user_id", "user123").
  WithEQ("status", "active").
  WithIndex("gsi_by_status")

input2, _ := query2.BuildQuery()
fmt.Printf("Forced: %s\n", *input2.IndexName)
// Output: Forced: gsi_by_status

Additional Notes

Without WithIndex:

  • QueryBuilder automatically selects the optimal index
  • Searches for a GSI/LSI that supports your keys

With WithIndex:

  • QueryBuilder forcibly uses the specified index
  • Ignores automatic selection

qb.StartFrom ​

Sets the starting key for pagination.

go
func (qb *QueryBuilder) StartFrom(
  lastEvaluatedKey map[string]types.AttributeValue,
) *QueryBuilder
Example
go
var lastKey map[string]types.AttributeValue

query1 := NewQueryBuilder().
    WithEQ("user_id", "123").
    Limit(10)

result1, err := dynamoClient.Query(ctx, query1Input)
lastKey = result1.LastEvaluatedKey

query2 := NewQueryBuilder().
    WithEQ("user_id", "123").
    StartFrom(lastKey).
    Limit(10)

LastEvaluatedKey can be null even if more data exists and the response size exceeds 1MB.

Always check for LastEvaluatedKey to continue pagination.

qb.OrderByDesc ​

Sets descending order.

go
func (qb *QueryBuilder) OrderByDesc() *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  OrderByDesc()

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

OrderByDesc only affects sorting by the sort key, not the filter results.

qb.OrderByAsc ​

Sets ascending order.

go
func (qb *QueryBuilder) OrderByAsc() *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  OrderByAsc()

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

OrderByAsc only affects sorting by the sort key, not the filter results.

qb.WithPreferredSortKey ​

Indicates to the index selection algorithm a preferred sort key.

go
func (qb *QueryBuilder) WithPreferredSortKey(key string) *QueryBuilder
Example
go
// There are multiple indexes with the same hash key:
// - lsi_by_status (sort key: status)  
// - lsi_by_created_at (sort key: created_at)
// - lsi_by_priority (sort key: priority)

query1 := userorders.NewQueryBuilder().
    WithEQ("user_id", "user123").
    WithEQ("status", "active")
// Can choose any matching index (e.g., lsi_by_status or lsi_by_created_at)

query2 := userorders.NewQueryBuilder().
    WithEQ("user_id", "user123").
    WithEQ("status", "active").
    WithPreferredSortKey("created_at")
// Hints to prefer lsi_by_created_at if applicable

items, err := query2.Execute(ctx, dynamoClient)

When to Use WithPreferredSortKey

Use WithPreferredSortKey when:

  • There are multiple indexes matching the query's partition key
  • You want the results to be sorted by a specific sort key
  • You know which index is more efficient or relevant for your use case

Important

WithPreferredSortKey Is a Hint, Not a Requirement

✅ The query planner prefers an index with the specified sort key
❌ But it may choose a different one if no suitable index is found
🎯 To force a specific index, use WithIndex(indexName) instead

qb.With ​

Adds a condition for DynamoDB queries.
Accepts:

  • field - field name
  • value - value
  • op - operator type
go
func (qb *QueryBuilder) With(
  field string, 
  op OperatorType, 
  values ...any,
) *QueryBuilder

Query impact:

All With methods are applied BEFORE reading data from DynamoDB.
(This is faster and cheaper than using Filter)

Example
go
query := NewQueryBuilder().With("user_id", EQ, "123")

queryInput, err := query.BuildQuery()
if err != nil {
    return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
    return err
}

for _, item := range items {
    fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}

Sugar ​

Methods are only generated when using the all generation type:

bash
godyno -s schema.json -o ./gen -mode all
godyno -s schema.json -o ./gen

In min mode, use the generic With method instead:

go
query
  .With("user_id", EQ, "123")
  .With("created_at", GT, timestamp)

query
  .With("status", BETWEEN, "active", "pending")
  .With("priority", LTE, 100)
qb.WithEQ ​

Adds an equal condition for keys.

go
func (qb *QueryBuilder) WithEQ(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  WithEQ("created_at", timestamp).

queryInput, err := query.BuildQuery()
if err != nil {
    return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
    return err
}

for _, item := range items {
    fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
qb.WithGT ​

Adds a greater than condition for the range key.

go
func (qb *QueryBuilder) WithGT(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithGT("created_at", yesterdayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.WithLT ​

Adds a less than condition for the range key.

go
func (qb *QueryBuilder) WithLT(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithLT("created_at", yesterdayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.WithGTE ​

Adds a greater than or equal to condition for the range key.

go
func (qb *QueryBuilder) WithGTE(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithGTE("created_at", yesterdayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.WithLTE ​

Adds a less than or equal to condition for the range key.

go
func (qb *QueryBuilder) WithLTE(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithLTE("created_at", yesterdayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.WithBetween ​

Adds a range condition for the range key.

go
func (qb *QueryBuilder) WithBetween(field string, start, end any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithBetween("created_at", yesterdayTimestamp, todayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.WithBeginsWith ​

Adds a begins with condition for the range key.

go
func (qb *QueryBuilder) WithBeginsWith(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().WithBeginsWith("created_at", yesterdayTimestamp)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

qb.WithProjection ​

Specifies which exact fields to return from DynamoDB instead of retrieving the entire item.

go
func (qb *QueryBuilder) WithProjection(attributes []string) *QueryBuilder
Example
go
query := NewQueryBuilder().
    WithEQ("user_id", "123").
    WithProjection([]string{"id", "email", "created_at"})

queryInput, err := query.BuildQuery()
if err != nil {
    return err
}

items, err := query.Execute(ctx, dynamoClient)
if err != nil {
    return err
}

for _, item := range items {
    fmt.Printf("ID: %s, Email: %s, Created: %s\n", 
        item.Id, item.Email, item.CreatedAt)
}

TIP

Without WithProjection:

go
type SchemaItem struct {
    Id          string   // ✅
    Name        string   // ✅ 
    Email       string   // ✅
    Description string   // ✅ (not needed, but will be returned)
    Content     string   // ✅ (not needed, but will be returned)
    Tags        []string // ✅ (not needed, but will be returned)
    ViewCount   int      // ✅ (not needed, but will be returned)
}

With WithProjection:

go
// Only the specified fields will be returned
WithProjection([]string{"id", "name", "email"})

// Resulting struct:
type PartialItem struct {
    Id    string  // ✅
    Name  string  // ✅
    Email string  // ✅
    // Description - omitted
    // Content - omitted  
    // Tags - omitted
    // ViewCount - omitted
}

Projection reduces bandwidth usage but does NOT reduce RCU cost — you're still billed for reading the full item.

qb.Filter ​

Adds a condition for filtering values retrieved from DynamoDB.
Accepts:

  • field - field name
  • value - value
  • op - operator type
go
func (qb *QueryBuilder) Filter(
  field string, 
  op OperatorType, 
  values ...any,
) *QueryBuilder

Query impact:

All Filter methods are applied AFTER reading data from DynamoDB.
(use with caution)

Example
go
query := NewQueryBuilder().
  With("user_id", EQ, "123").
  Filter("status", CONTAINS, "active")

queryInput, err := query.BuildQuery()
if err != nil {
    return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
    return err
}

for _, item := range items {
    fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}

Sugar ​

Methods are only generated when using the all generation type:

bash
godyno -s schema.json -o ./gen -mode all
godyno -s schema.json -o ./gen

In min mode, use the generic Filter method instead:

go
query
  .Filter("status", EQ, "active")
  .Filter("priority", BETWEEN, 80, 100)
qb.FilterEQ ​

Adds an equality filter.

go
func (qb *QueryBuilder) FilterEQ(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterEQ("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterNE ​

Adds an inequality filter.

go
func (qb *QueryBuilder) FilterNE(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterNE("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterGT ​

Adds a greater than filter.

go
func (qb *QueryBuilder) FilterGT(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterGT("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterLT ​

Adds a less than filter.

go
func (qb *QueryBuilder) FilterLT(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterLT("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterGTE ​

Adds a greater than or equal to filter.

go
func (qb *QueryBuilder) FilterGTE(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterGTE("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterLTE ​

Adds a less than or equal to filter.

go
func (qb *QueryBuilder) FilterLTE(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterLTE("age", 18)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterBetween ​

Adds a range filter.

go
func (qb *QueryBuilder) FilterBetween(field string, start, end any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterBetween("age", 18, 35)

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterContains ​

Adds a contains filter.

go
func (qb *QueryBuilder) FilterContains(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterContains("email", "@gmail.com")

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterNotContains ​

Adds a not contains filter.

go
func (qb *QueryBuilder) FilterNotContains(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterNotContains("email", "@gmail.com")

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterBeginsWith ​

Adds a begins with filter.

go
func (qb *QueryBuilder) FilterBeginsWith(field string, value any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterBeginsWith("email", "alex")

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterIn ​

Adds an in list filter.

go
func (qb *QueryBuilder) FilterIn(field string, values ...any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterIn("email", []string{"alex@gmail.com", "john@gmail.com"})

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterNotIn ​

Adds a not in list filter.

go
func (qb *QueryBuilder) FilterNotIn(field string, values ...any) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterNotIn("email", []string{"alex@gmail.com", "john@gmail.com"})

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterExists ​

Adds a field exists filter.

go
func (qb *QueryBuilder) FilterExists(field string) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterExists("email")

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
qb.FilterNotExists ​

Adds a field does not exist filter.

go
func (qb *QueryBuilder) FilterNotExists(field string) *QueryBuilder
Example
go
query := NewQueryBuilder().
  WithEQ("user_id", "123").
  FilterNotExists("email")

queryInput, err := query.BuildQuery()
if err != nil {
  return err
}
items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

qb.BuildQuery ​

Builds a DynamoDB QueryInput.

go
func (qb *QueryBuilder) BuildQuery() (*dynamodb.QueryInput, error)

qb.Execute ​

Executes the query.

go
func (qb *QueryBuilder) Execute(
  ctx context.Context, 
  client *dynamodb.Client,
) (
  []SchemaItem, 
  error,
)

ScanBuilder ​

Scan reads the entire table.

NewScanBuilder ​

Create new ScanBuilder.

go
func NewScanBuilder() *ScanBuilder

sb.WithIndex ​

Explicitly specifies which secondary index to use for the query, overriding automatic index selection.

go
func (sb *ScanBuilder) WithIndex(indexName string) *ScanBuilder

Performs a scan on a specific index

  • GSI (Global Secondary Index) has its own RCU/WCU configuration
  • LSI (Local Secondary Index) shares RCU/WCU with the base table
Example
go
scan := NewScanBuilder().
  WithIndex("status-index").
  FilterEQ("status", "active")

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}

sb.Limit ​

Sets the maximum number of items.

go
func (sb *ScanBuilder) Limit(limit int) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterEQ("status", "active").
  Limit(10)

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}

sb.StartFrom ​

Sets the starting key for pagination.

go
func (sb *ScanBuilder) StartFrom(
  lastEvaluatedKey map[string]types.AttributeValue,
) *ScanBuilder

Pagination

LastEvaluatedKey can be null even if there is more data and the response size exceeds 1MB.

Always check for LastEvaluatedKey to continue pagination.

Example
go
var lastKey map[string]types.AttributeValue

scan1 := NewScanBuilder().
   FilterEQ("status", "active").
   Limit(10)

result1, err := dynamoClient.Scan(ctx, scan1Input)
lastKey = result1.LastEvaluatedKey

scan2 := NewScanBuilder().
   FilterEQ("status", "active").
   StartFrom(lastKey).
   Limit(10)

sb.WithProjection ​

Specifies which exact fields to return from DynamoDB instead of all item attributes.

go
func (sb *ScanBuilder) WithProjection(attributes []string) *ScanBuilder

INFO

Without WithProjection:

go
type SchemaItem struct {
    Id          string   // ✅
    Name        string   // ✅ 
    Email       string   // ✅
    Description string   // ✅ (not needed, but will be returned)
    Content     string   // ✅ (not needed, but will be returned)
    Tags        []string // ✅ (not needed, but will be returned)
    ViewCount   int      // ✅ (not needed, but will be returned)
}

With WithProjection:

go
// Returns ONLY the specified fields
WithProjection([]string{"id", "name", "email"})

// As a result, only:
type PartialItem struct {
    Id    string  // ✅
    Name  string  // ✅
    Email string  // ✅
    // Description - missing
    // Content - missing  
    // Tags - missing
    // ViewCount - missing
}

Projection reduces bandwidth usage but does NOT reduce RCU — you are billed for reading all item attributes.

Example
go
scan := NewScanBuilder().
   FilterEQ("status", "active").
   WithProjection([]string{"id", "email", "created_at"})

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
   return err
}

for _, item := range items {
   fmt.Printf("ID: %s, Email: %s, Created: %s\n", 
       item.Id, item.Email, item.CreatedAt)
}

sb.WithParallelScan ​

go
func (sb *ScanBuilder) WithParallelScan(
  totalSegments, 
  segment int,
) *ScanBuilder

Parallel Scan

Increases RCU consumption proportionally to the number of segments.

Use with caution in production environments.

sb.Filter ​

Adds a condition to filter the values retrieved from DynamoDB.
Accept:

  • field - field name
  • value - value
  • op - operator type
go
func (sb *ScanBuilder) Filter(
  field string, 
  op OperatorType, 
  values ...any,
) *ScanBuilder
Example
go
scan := NewScanBuilder().
  Filter("user_id", EQ, "123").
  Filter("status", CONTAINS, "active")

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}

Sugar ​

Methods are only generated when using the all generation type:

bash
godyno -s schema.json -o ./gen -mode all
godyno -s schema.json -o ./gen

In min mode, use the generic Filter method instead:

go
scan
  .Filter("status", EQ, "active")
  .Filter("priority", BETWEEN, 80, 100)
sb.FilterEQ ​

Adds an equality filter.

go
func (sb *ScanBuilder) FilterEQ(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterEQ("user_id", "123").

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterNE ​

Adds a not equal filter.

go
func (sb *ScanBuilder) FilterNE(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterNE("user_id", "123").

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterGT ​

Adds a greater than filter.

go
func (sb *ScanBuilder) FilterGT(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterGT("age", 18).

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterLT ​

Adds a less than filter.

go
func (sb *ScanBuilder) FilterLT(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterLT("age", 18).

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterGTE ​

Adds a greater than or equal filter.

go
func (sb *ScanBuilder) FilterGTE(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterGTE("age", 18).

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterLTE ​

Adds a less than or equal filter.

go
func (sb *ScanBuilder) FilterLTE(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterLTE("age", 18).

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterBetween ​

Adds a between filter.

go
func (sb *ScanBuilder) FilterBetween(
  field string, 
  start, 
  end any,
) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterBetween("age", 18, 35).

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterContains ​

Adds a contains filter.

go
func (sb *ScanBuilder) FilterContains(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterContains("email", "@gmail.com").

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterNotContains ​

Adds a not contains filter.

go
func (sb *ScanBuilder) FilterNotContains(
  field string, 
  value any,
) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterContains("email", "@gmail.com").

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterBeginsWith ​

Adds a begins with filter.

go
func (sb *ScanBuilder) FilterBeginsWith(field string, value any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterBeginsWith("email", "alex").

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Status: %s\n", item.UserId, item.Status)
}
sb.FilterIn ​

Adds an IN list filter.

go
func (sb *ScanBuilder) FilterIn(field string, values ...any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterIn("email", []string{"alex@gmail.com", "john@gmail.com"})

items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
sb.FilterNotIn ​

Adds a NOT IN list filter.

go
func (sb *ScanBuilder) FilterNotIn(field string, values ...any) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterNotIn("email", []string{"alex@gmail.com", "john@gmail.com"})

items, err := query.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
sb.FilterExists ​

Adds a NOT NULL filter.

go
func (sb *ScanBuilder) FilterExists(field string) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterExists("email")

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}
sb.FilterNotExists ​

Adds a Empty filter.

go
func (sb *ScanBuilder) FilterNotExists(field string) *ScanBuilder
Example
go
scan := NewScanBuilder().
  FilterNotExists("email")

items, err := scan.Execute(ctx, dynamoClient)
if err != nil {
  return err
}

for _, item := range items {
  fmt.Printf("User: %s, Created: %s\n", item.UserId, item.CreatedAt)
}

sb.BuildScan ​

Builds a DynamoDB ScanInput.

go
func (sb *ScanBuilder) BuildScan() (*dynamodb.ScanInput, error)

sb.Execute ​

Executes the scan operation.

go
func (sb *ScanBuilder) Execute(
  ctx context.Context, 
  client *dynamodb.Client,
) (
  []SchemaItem, 
  error,
)

Input Functions ​

ItemInput ​

Converts a SchemaItem into a DynamoDB AttributeValue map.

go
func ItemInput(item SchemaItem) (map[string]types.AttributeValue, error)

KeyInput ​

Creates a key from hash and range key values.

go
func KeyInput(
  hashKeyValue, 
  rangeKeyValue any,
) (
  map[string]types.AttributeValue, 
  error,
)

rangeKeyValue can be nil if the table uses only a hash key_

KeyInputFromRaw ​

Creates a key from raw values with validation.

go
func KeyInputFromRaw(
  hashKeyValue, 
  rangeKeyValue any,
) (
  map[string]types.AttributeValue, 
  error,
)

KeyInputFromItem ​

Extracts the key from a SchemaItem.

go
func KeyInputFromItem(
  item SchemaItem
) (
  map[string]types.AttributeValue, 
  error,
)

UpdateItemInput ​

Converts a SchemaItem into a DynamoDB UpdateItemInput.

go
UpdateItemInput(item SchemaItem) (*dynamodb.DeleteItemInput, error)

UpdateItemInputFromRaw ​

Creates an UpdateItemInput from raw values.

go
func UpdateItemInputFromRaw(
  hashKeyValue, 
  rangeKeyValue any, 
  updates map[string]any,
) (
  *dynamodb.UpdateItemInput, 
  error,
)

UpdateItemInputWithCondition ​

Creates an UpdateItemInput with a condition expression.

go
func UpdateItemInputWithCondition(
  hashKeyValue, 
  rangeKeyValue any, 
  updates map[string]any, 
  conditionExpression string, 
  conditionAttributeNames map[string]string, 
  conditionAttributeValues map[string]types.AttributeValue,
) (
  *dynamodb.UpdateItemInput, 
  error,
)

UpdateItemInputWithExpression ​

Creates an UpdateItemInput using expression builders.

go
func UpdateItemInputWithExpression(
  hashKeyValue, 
  rangeKeyValue any, 
  updateBuilder expression.UpdateBuilder, 
  conditionBuilder *expression.ConditionBuilder,
) (
  *dynamodb.UpdateItemInput, 
  error,
)

DeleteItemInput ​

Converts a SchemaItem into a DynamoDB DeleteItemInput.

go
DeleteItemInput(item SchemaItem) (*dynamodb.DeleteItemInput, error)

DeleteItemInputFromRaw ​

Creates a DeleteItemInput from key values.

go
func DeleteItemInputFromRaw(
  hashKeyValue, 
  rangeKeyValue any,
) (
  *dynamodb.DeleteItemInput, 
  error,
)

DeleteItemInputWithCondition ​

Creates a DeleteItemInput with a condition expression.

go
func DeleteItemInputWithCondition(
  hashKeyValue, 
  rangeKeyValue any, 
  conditionExpression string, 
  expressionAttributeNames map[string]string, 
  expressionAttributeValues map[string]types.AttributeValue,
) (
  *dynamodb.DeleteItemInput, 
  error,
)

BatchItemsInput ​

Converts a slice of SchemaItem into a slice of AttributeValue maps.

go
func BatchItemsInput(
  items []SchemaItem,
) (
  []map[string]types.AttributeValue, 
  error,
)

Maximum 25 items per batch operation.

Exceeding the limit will result in an error.

BatchDeleteItemsInput ​

Creates BatchWriteItemInput for deleting items.

go
func BatchDeleteItemsInput(
  keys []map[string]types.AttributeValue,
) (
  *dynamodb.BatchWriteItemInput, 
  error,
)

Maximum of 25 items per batch operation.

Exceeding the limit will result in an error.

BatchDeleteItemsInputFromRaw ​

Creates BatchWriteItemInput from SchemaItems.

go
func BatchDeleteItemsInputFromRaw(
  items []SchemaItem,
) (
  *dynamodb.BatchWriteItemInput, 
  error,
)

Maximum of 25 items per batch operation.

Exceeding the limit will result in an error.

Stream Functions ​

Methods are generated only when using the all generation type.

bash
godyno -s schema.json -o ./gen -mode all
godyno -s schema.json -o ./gen

ExtractFromDynamoDBStreamEvent ​

Extracts the new state of the item from a stream record.

go
func ExtractFromDynamoDBStreamEvent(dbEvent events.DynamoDBEventRecord) (*SchemaItem, error)

ExtractOldFromDynamoDBStreamEvent ​

Extracts the old state of the item from a stream record.

go
func ExtractOldFromDynamoDBStreamEvent(dbEvent events.DynamoDBEventRecord) (*SchemaItem, error)

ExtractBothFromDynamoDBStreamEvent ​

Extracts the old and new state of the item from a stream record.

go
func ExtractBothFromDynamoDBStreamEvent(
  dbEvent events.DynamoDBEventRecord,
) (
  *SchemaItem, 
  *SchemaItem, 
  error,
)

CreateTriggerHandler ​

Create DynamoDB Event Handler.

go
func CreateTriggerHandler(
  onInsert func(context.Context, *SchemaItem) error,
  onModify func(context.Context, *SchemaItem, *SchemaItem) error,
  onDelete func(context.Context, map[string]events.DynamoDBAttributeValue) error,
) func(ctx context.Context, event events.DynamoDBEvent) error

TIP

  • onInsert — called for INSERT events, receives the new SchemaItem
  • onModify — called for MODIFY events, receives the old and new SchemaItem
  • onDelete — called for REMOVE events, receives the keys of the deleted item

IsFieldModified ​

Checks whether a given attribute was actually changed in a DynamoDB MODIFY stream event. It compares the old and new images and returns true only if the field was added, removed, or its value differs.

go
func IsFieldModified(
  record events.DynamoDBEventRecord,
  fieldName string,
) bool

return true if:

  • the event is MODIFY and the field previously did not exist but now does
  • the event is MODIFY and the field previously existed but now does not
  • the event is MODIFY and the field existed in both images and its serialized value differs

Operators ​

Key Conditions VS Filters

Key Conditions - applied BEFORE reading:

  • Define which items to read from DynamoDB
  • Affect the cost of the operation (RCU)
  • Only support: [EQ, GT, LT, GTE, LTE, BETWEEN, BEGINS_WITH]
  • EQ is required for the partition key
  • Other operators apply only to the sort key

Filter Expressions - applied AFTER reading:

  • Filter the data after it has been read
  • Do NOT affect the cost (you pay for all read items)
  • Support ALL operators
  • Filter-only operators: [CONTAINS, NOT_CONTAINS, IN, NOT_IN, EXISTS, NOT_EXISTS, NE]

Recommendation:

Use key conditions as much as possible, and filters only for additional refinement.

OperatorType ​

go
type OperatorType string

Constants ​

go
const (
  EQ          OperatorType = "="
  NE          OperatorType = "<>"
  GT          OperatorType = ">"
  LT          OperatorType = "<"
  GTE         OperatorType = ">="
  LTE         OperatorType = "<="
  BETWEEN     OperatorType = "BETWEEN"
  CONTAINS    OperatorType = "CONTAINS"
  NOT_CONTAINS OperatorType = "NOT_CONTAINS"
  BEGINS_WITH OperatorType = "BEGINS_WITH"
  IN          OperatorType = "IN"
  NOT_IN      OperatorType = "NOT_IN"
  EXISTS      OperatorType = "EXISTS"
  NOT_EXISTS  OperatorType = "NOT_EXISTS"
)

ValidateValues ​

Validates the number of values for an operator.

go
func ValidateValues(op OperatorType, values []any) bool

IsKeyConditionOperator ​

Checks if the operator can be used in key conditions.

go
func IsKeyConditionOperator(op OperatorType) bool

ValidateOperator ​

Checks if the operator is compatible with the field.

go
func ValidateOperator(fieldName string, op OperatorType) bool

BuildConditionExpression ​

Creates a filter condition.

go
func BuildConditionExpression(
  field string, 
  op OperatorType, 
  values []any,
) (
  expression.ConditionBuilder, 
  error,
)

BuildKeyConditionExpression ​

Creates a key condition.

go
func BuildKeyConditionExpression(
  field string, 
  op OperatorType, 
  values []any,
) (
  expression.KeyConditionBuilder, 
  error,
)

Released under the MIT License.

Copyright © 2025 Mad-Pixels