[Go] add Release, Reserve and Resize to array.Builder interface

Author: sbinet

go/arrow/array/builder.go

@@ -31,6 +31,10 @@ const (
 
 // Builder provides an interface to build arrow arrays.
 type Builder interface {
+	// Retain increases the reference count by 1.
+	// Retain may be called simultaneously from multiple goroutines.
+	Retain()
+
 	// Release decreases the reference count by 1.
 	Release()
 
@@ -47,6 +51,14 @@ type Builder interface {
 	// AppendNull adds a new null value to the array being built.
 	AppendNull()
 
+	// Reserve ensures there is enough space for appending n elements
+	// by checking the capacity and calling Resize if necessary.
+	Reserve(n int)
+
+	// Resize adjusts the space allocated by b to n elements. If n is greater than b.Cap(),
+	// additional memory will be allocated. If n is smaller, the allocated memory may reduced.
+	Resize(n int)
+
 	// NewArray creates a new array from the memory buffers used
 	// by the builder and resets the Builder so it can be used to build
 	// a new array.

go/arrow/array/null.go

@@ -86,10 +86,13 @@ func (b *NullBuilder) AppendNull() {
 	b.builder.nulls++
 }
 
+func (*NullBuilder) Reserve(size int) {}
+func (*NullBuilder) Resize(size int)  {}
+
 func (*NullBuilder) init(cap int)                       {}
 func (*NullBuilder) resize(newBits int, init func(int)) {}
 
-// NewArray creates a List array from the memory buffers used by the builder and resets the NullBuilder
+// NewArray creates a Null array from the memory buffers used by the builder and resets the NullBuilder
 // so it can be used to build a new array.
 func (b *NullBuilder) NewArray() Interface {
 	return b.NewNullArray()