zeroshade commented on issue #46555: URL: https://github.com/apache/arrow/issues/46555#issuecomment-2904786416
I've been building out an API for a Variant Builder for the Go implementation, and so far I have based it on the [Spark Variant Builder](https://github.com/apache/spark/blob/master/common/variant/src/main/java/org/apache/spark/types/variant/VariantBuilder.java). The API looks like this for the primitive types: ```go func (b *Builder) AppendNull() error {...} func (b *Builder) AppendBool(v bool) error {...} // uses the smallest int type it can based on the value func (b *Builder) AppendInt(v int64) error {...} func (b *Builder) AppendTimestamp(v arrow.Timestamp, useMicro, useUTC bool) error {...} // and so on.... ``` There are also methods for adding a key to the metadata: ```go func (b *Builder) AddKey(k string) (id uint32) {...} func (b *Builder) AddKeys(k []string) (id []uint32) {...} ``` Which just adds them so they will get put into the metadata when you finally build it, and returns the IDs. For managing objects and arrays, I decided against using sub-builders as that would require having to manage the lifetime of multiple objects and sub-builders which could get very complex. Instead the pattern is the following: 1. Get the starting offset via `Buffer.Offset()` 2. Use the starting offset and helper functions to build a list of fields/offsets while appending the values 3. Call `FinishArray` / `FinishObject` with the start offset + list of offsets/fields. Code-wise it looks like this to build a list: ```go var b variant.Builder start := b.Offset() offsets := make([]int, 0) offsets = append(offsets, b.NextElement(start)) b.AppendInt(5) offsets = append(offsets, b.NextElement(start)) b.AppendBool(true) offsets = append(offsets, b.NextElement(start)) b.AppendInt(9) b.FinishArray(start, offsets) v, err := b.Build() ``` Resulting in a variant that is equivalent to `[5, true, 9]`. For an object it looks like: ```go var b variant.Builder start := b.Offset() fields := make([]variant.FieldEntry, 0) fields := append(fields, b.NextField(start, "int_field")) b.AppendInt(1) fields = append(fields, b.NextField(start, "string_field")) b.AppendString("Variant") fields = append(fields, b.NextField(start, "null_field")) b.AppendNull() b.FinishObject(start, fields) v, err := b.Build() ``` This would create a variant that is equivalent to `{ "int_field": 1, "string_field": "Variant", "null_field": null }` What do you think? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
