support on-demand billing mode in CreateTable and UpdateTable

also table Description
(resolves #87)

createtable.go

@@ -49,6 +49,7 @@ type CreateTable struct {
 	readUnits     int64
 	writeUnits    int64
 	streamView    StreamView
+	ondemand      bool
 	err           error
 }
 
@@ -81,8 +82,15 @@ func (db *DB) CreateTable(name string, from interface{}) *CreateTable {
 	return ct
 }
 
+// OnDemand specifies to create the table with on-demand (pay per request) billing mode,
+// if enabled. On-demand mode is disabled by default.
+func (ct *CreateTable) OnDemand(enabled bool) *CreateTable {
+	ct.ondemand = enabled
+	return ct
+}
+
 // Provision specifies the provisioned read and write capacity for this table.
-// If Provision isn't called, the table will be created with 1 unit each.
+// If Provision isn't called and on-demand mode is disabled, the table will be created with 1 unit each.
 func (ct *CreateTable) Provision(readUnits, writeUnits int64) *CreateTable {
 	ct.readUnits, ct.writeUnits = readUnits, writeUnits
 	return ct
@@ -283,10 +291,14 @@ func (ct *CreateTable) input() *dynamodb.CreateTableInput {
 		TableName:            &ct.tableName,
 		AttributeDefinitions: ct.attribs,
 		KeySchema:            ct.schema,
-		ProvisionedThroughput: &dynamodb.ProvisionedThroughput{
+	}
+	if ct.ondemand {
+		input.BillingMode = aws.String(dynamodb.BillingModePayPerRequest)
+	} else {
+		input.ProvisionedThroughput = &dynamodb.ProvisionedThroughput{
 			ReadCapacityUnits:  &ct.readUnits,
 			WriteCapacityUnits: &ct.writeUnits,
-		},
+		}
 	}
 	if ct.streamView != "" {
 		enabled := true
@@ -324,7 +336,9 @@ func (ct *CreateTable) input() *dynamodb.CreateTableInput {
 				ProjectionType: &all,
 			}
 		}
-		if idx.ProvisionedThroughput == nil {
+		if ct.ondemand {
+			idx.ProvisionedThroughput = nil
+		} else if idx.ProvisionedThroughput == nil {
 			units := int64(1)
 			idx.ProvisionedThroughput = &dynamodb.ProvisionedThroughput{
 				ReadCapacityUnits:  &units,

describetable.go

@@ -23,6 +23,8 @@ type Description struct {
 
 	// Provisioned throughput for this table.
 	Throughput Throughput
+	// OnDemand is true if on-demand (pay per request) billing mode is enabled.
+	OnDemand bool
 
 	// The number of items of the table, updated every 6 hours.
 	Items int64
@@ -104,6 +106,10 @@ func newDescription(table *dynamodb.TableDescription) Description {
 	desc.HashKeyType = lookupADType(table.AttributeDefinitions, desc.HashKey)
 	desc.RangeKeyType = lookupADType(table.AttributeDefinitions, desc.RangeKey)
 
+	if table.BillingModeSummary != nil && table.BillingModeSummary.BillingMode != nil {
+		desc.OnDemand = *table.BillingModeSummary.BillingMode == dynamodb.BillingModePayPerRequest
+	}
+
 	if table.ProvisionedThroughput != nil {
 		desc.Throughput = newThroughput(table.ProvisionedThroughput)
 	}

updatetable.go

@@ -13,6 +13,8 @@ type UpdateTable struct {
 	table Table
 	r, w  int64 // throughput
 
+	billingMode *string
+
 	disableStream bool
 	streamView    StreamView
 
@@ -32,6 +34,17 @@ func (table Table) UpdateTable() *UpdateTable {
 	}
 }
 
+// OnDemand sets this table to use on-demand (pay per request) billing mode if enabled is true.
+// If enabled is false, this table will be changed to provisioned billing mode.
+func (ut *UpdateTable) OnDemand(enabled bool) *UpdateTable {
+	if enabled {
+		ut.billingMode = aws.String(dynamodb.BillingModePayPerRequest)
+	} else {
+		ut.billingMode = aws.String(dynamodb.BillingModeProvisioned)
+	}
+	return ut
+}
+
 // Provision sets this table's read and write throughput capacity.
 func (ut *UpdateTable) Provision(read, write int64) *UpdateTable {
 	ut.r, ut.w = read, write
@@ -45,7 +58,8 @@ func (ut *UpdateTable) ProvisionIndex(name string, read, write int64) *UpdateTab
 }
 
 // CreateIndex adds a new secondary global index.
-// You must specify the index name, keys, key types, projection, and throughput.
+// You must specify the index name, keys, key types, projection.
+// If this table is not on-demand you must also specify throughput.
 func (ut *UpdateTable) CreateIndex(index Index) *UpdateTable {
 	if index.Name == "" {
 		ut.err = errors.New("dynamo: update table: missing index name")
@@ -62,9 +76,6 @@ func (ut *UpdateTable) CreateIndex(index Index) *UpdateTable {
 	if index.ProjectionType == "" {
 		ut.err = errors.New("dynamo: update table: missing projection type")
 	}
-	if index.Throughput.Read < 1 || index.Throughput.Write < 1 {
-		ut.err = errors.New("dynamo: update table: throughput read and write must be 1 or more")
-	}
 
 	ut.addAD(index.HashKey, index.HashKeyType)
 	if index.RangeKey != "" {
@@ -124,6 +135,7 @@ func (ut *UpdateTable) input() *dynamodb.UpdateTableInput {
 	input := &dynamodb.UpdateTableInput{
 		TableName:            aws.String(ut.table.Name()),
 		AttributeDefinitions: ut.ads,
+		BillingMode:          ut.billingMode,
 	}
 
 	if ut.r != 0 || ut.w != 0 {
@@ -196,14 +208,16 @@ func createIndexAction(index Index) *dynamodb.CreateGlobalSecondaryIndexAction {
 	add := &dynamodb.CreateGlobalSecondaryIndexAction{
 		IndexName: &index.Name,
 		KeySchema: ks,
-		ProvisionedThroughput: &dynamodb.ProvisionedThroughput{
-			ReadCapacityUnits:  aws.Int64(index.Throughput.Read),
-			WriteCapacityUnits: aws.Int64(index.Throughput.Write),
-		},
 		Projection: &dynamodb.Projection{
 			ProjectionType: aws.String((string)(index.ProjectionType)),
 		},
 	}
+	if index.Throughput.Read > 0 && index.Throughput.Write > 0 {
+		add.ProvisionedThroughput = &dynamodb.ProvisionedThroughput{
+			ReadCapacityUnits:  aws.Int64(index.Throughput.Read),
+			WriteCapacityUnits: aws.Int64(index.Throughput.Write),
+		}
+	}
 	if index.ProjectionType == IncludeProjection {
 		add.Projection.NonKeyAttributes = aws.StringSlice(index.ProjectionAttribs)
 	}