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Posted to github@arrow.apache.org by "sundy-li (via GitHub)" <gi...@apache.org> on 2023/05/28 04:40:05 UTC
[GitHub] [arrow-rs] sundy-li opened a new pull request, #4299: chore: export fn parquet_to_array_schema_and_fields
sundy-li opened a new pull request, #4299:
URL: https://github.com/apache/arrow-rs/pull/4299
# Which issue does this PR close?
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Closes 4298
# Rationale for this change
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# What changes are included in this PR?
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export fn parquet_to_array_schema_and_fields
# Are there any user-facing changes?
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[GitHub] [arrow-rs] sundy-li commented on pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "sundy-li (via GitHub)" <gi...@apache.org>.
sundy-li commented on PR #4299:
URL: https://github.com/apache/arrow-rs/pull/4299#issuecomment-1567110449
Thanks, we'd like that arrow-rs could expose some api to cover this method.
https://github.com/datafuselabs/databend/blob/529d184808eecbf1cd09ce31f3629553478f8ef2/src/query/storages/fuse/src/io/read/block/block_reader_parquet_deserialize.rs#L86-L172
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[GitHub] [arrow-rs] sundy-li commented on pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "sundy-li (via GitHub)" <gi...@apache.org>.
sundy-li commented on PR #4299:
URL: https://github.com/apache/arrow-rs/pull/4299#issuecomment-1566325254
Because we don't need the high-level api to read the metadata. The metadata is stored outside parquet files in our database system. Once the metadata and rowgroup index are reader, rowgroups are pruned and we only need to read the data by row-group with Bytes of each column.
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[GitHub] [arrow-rs] tustvold commented on pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold commented on PR #4299:
URL: https://github.com/apache/arrow-rs/pull/4299#issuecomment-1566271541
I'm a little apprehensive about exposing these APIs, they are fairly low-level and not really designed to be part of the public API surface. The issue states
> We want to use some low-level APIs to read parquet files by rowgroup
The higher-level APIs support [filtering by row group](https://docs.rs/parquet/latest/parquet/arrow/arrow_reader/struct.ArrowReaderBuilder.html#method.with_row_groups), among other things. Is there a particular piece of functionality that is missing from this?
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[GitHub] [arrow-rs] tustvold commented on pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "tustvold (via GitHub)" <gi...@apache.org>.
tustvold commented on PR #4299:
URL: https://github.com/apache/arrow-rs/pull/4299#issuecomment-1566695201
You can override how metadata is loaded by providing a custom AsynFileReader? Is this insufficient?
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[GitHub] [arrow-rs] sundy-li commented on pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "sundy-li (via GitHub)" <gi...@apache.org>.
sundy-li commented on PR #4299:
URL: https://github.com/apache/arrow-rs/pull/4299#issuecomment-1567035679
Yes, `AsyncFileReader`'s `get_metadata` can work.
But:
1. We don't store the whole metadata of the parquet files, we just store the `Vec<ColumnChunkMetaData>` of each leaf column, because we only write one row group, so it's much simple and small metadata.
2. The `ParquetRecordBatchStream` will be reading IO task in dedicated async runtime and decoding in blocking threads. But we have completely separated the two processes, we will first fetch the Bytes in dedicated async runtime and send the results to a thread pool to decode them into arrrays.
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[GitHub] [arrow-rs] sundy-li closed pull request #4299: chore: export fn parquet_to_array_schema_and_fields
Posted by "sundy-li (via GitHub)" <gi...@apache.org>.
sundy-li closed pull request #4299: chore: export fn parquet_to_array_schema_and_fields
URL: https://github.com/apache/arrow-rs/pull/4299
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