feat: Honor compression settings for metadata.json on write by emkornfield · Pull Request #1876 · apache/iceberg-rust

emkornfield · 2025-11-19T22:13:09Z

Which issue does this PR close?

Split off from #1851

Partially fixes [Bug] iceberg-rust does not respect compression settings for metadata & avro #1731.

What changes are included in this PR?

This change honors the compression setting for metadata.json file (write.metadata.compression-codec).

Are these changes tested?

Add unit test to verify files are gzipped when the flag is enabled.

BREAKING CHANGE: Make write_to take MetadataLocation

Previously these properties where not honored on tabel properties. - Adds table properties for these values. - Plumbs them through for writers.

emkornfield · 2025-11-19T22:13:22Z

CC @kevinjqliu @liurenjie1024

liurenjie1024 · 2025-11-20T10:17:51Z

crates/iceberg/src/spec/table_properties.rs

    key: &str,
    default: T,
-) -> Result<T, anyhow::Error>
+) -> crate::error::Result<T>


Suggested change

) -> crate::error::Result<T>

) -> Result<T>

Unnecessary fully qualified name.

liurenjie1024 · 2025-11-20T10:19:58Z

crates/iceberg/src/spec/table_properties.rs

    /// The target file size for files.
    pub write_target_file_size_bytes: usize,
+    /// Compression codec for metadata files (JSON)
+    pub metadata_compression_codec: String,


This should be sth like Option<String>, none should be None in memory.

liurenjie1024 · 2025-11-20T10:29:36Z

crates/iceberg/src/spec/table_metadata.rs

+
+                // Modify filename to add .gz before .metadata.json
+                let location = metadata_location.as_ref();
+                let new_location = if location.ends_with(".metadata.json") {


I don't think we should simply replace the suffix with this approach. Currently all metadata location generated logic are in MetadataLocation, we should add a new method in like following and deprecate old method as following:

impl MetadataLocation { #[deprecate("Use new_with_table instead.")] pub fn new_with_table_location(table_location: impl ToString) -> Self { } pub fn new_with_table(table: &Table) -> Self { .... }

The table option seemed a little awkward with the control flow on how it is used istead I added a method that takes table properties. Also added a similar method for incrementing the number.

I modified this logic a bit and kept. My concern here is if we only deprecate the new_with_table_location then users can write out metadata.json files in a format that would be unreadable by other readers.

crates/catalog/s3tables/src/catalog.rs

kevinjqliu

Generally LGTM, a few nit comments.
would be good to get a second pair of 👀

crates/iceberg/src/spec/table_properties.rs

kevinjqliu · 2025-11-21T03:45:28Z

crates/iceberg/src/catalog/metadata_location.rs

+
+    /// Creates a completely new metadata location starting at version 0,
+    /// with compression settings from the table's properties.
+    /// Only used for creating a new table. For updates, see `with_next_version`.


Suggested change

/// Only used for creating a new table. For updates, see `with_next_version`.

/// Only used for creating a new table. For updates, see `with_next_version_and_properties`.

since with_next_version is also deprecated

I'll wait till I understand @liurenjie1024 concerns about with_next_version_and_properties to update this.

crates/catalog/s3tables/src/catalog.rs

liurenjie1024

Thanks @emkornfield for this pr, looks much better now, still need some refinements.

crates/iceberg/src/catalog/metadata_location.rs

liurenjie1024 · 2025-11-21T10:09:16Z

crates/iceberg/src/catalog/metadata_location.rs

+    /// Creates a new metadata location for an updated metadata file.
+    /// Takes table properties to determine compression settings, which may have changed
+    /// from the previous version.
+    pub fn with_next_version_and_properties(&self, properties: &HashMap<String, String>) -> Self {


We don't need this.

Can you clarify what you mean by we don't need it? I updated crates/iceberg/src/catalog/mod.rs to use it, if new properties change compression settings, I'm not sure how this would be reflected otherwise? I might have missed it but I don't think there is anything in the spec that prevents users from changing compression properties.

If properties has been changes, we should build a new instance of this MetadataLocation struct.

If properties has been changes, we should build a new instance of this MetadataLocation struct.

My main concern here, is I don't think this is something that clients of MetadataLocation would actually understand and check for a new version of the metadata (i.e. the path of least resistance is to call with_next_version on whatever metadata they used for creation. As a solution, I've created a static factory next_version which combines the two steps for the only call-site that exists for with_next_version. If you think it is better to not deprecated with_next_version I can also revert this change.

crates/iceberg/src/catalog/metadata_location.rs

Co-authored-by: Kevin Liu <kevinjqliu@users.noreply.github.com>

…nfield/iceberg-rust into feat/metadata-compression

) ## Which issue does this PR close? As discussed in the PR for [allowing compressed metadata.json](#1876 (comment)) writes we want CompressionCodec in a central place so it can be used in puffin and for other compression use-cases. Happy to move it to `spec/` as suggested in the original comment but this seemed more natural. ## What changes are included in this PR? This moves compression.rs to a top level (seems like the best location for common code but please let me know if there is a better place. - It adds Gzip as a compression option and replaces current direct use the GzEncoder package. - It adds validation to puffin that Gzip is not currently supported (per spec) ## Are these changes tested? Added unit tests to cover additions and existing tests cover the rest.

…pression

blackmwk

Thanks @emkornfield for this pr, we are quite close !

crates/iceberg/src/catalog/metadata_location.rs

crates/iceberg/src/spec/table_metadata.rs

crates/catalog/s3tables/src/catalog.rs

emkornfield · 2026-02-02T04:03:57Z

@blackmwk thanks for the review I think we need to close on a direct for this: https://github.com/apache/iceberg-rust/pull/1876/files#r2752454670

I'll separate out the S3 fix into its own PR.
Use the new compression enum on MetadataLocation.

If we can make breaking changes then:

Then if write-to takes metadata location then we don't need to store compression codec on MetadataLocation at all (we can make it take a compression codec when generating the final path). (I actually need to double check this, there might be other places that try to reserialize the string).
We can eliminate a lot of the validation logic.

blackmwk · 2026-02-03T01:04:40Z

Hi, @emkornfield

I'll separate out the S3 fix into its own PR.
Use the new compression enum on MetadataLocation.

I think this is the right direction to go.

If we can make breaking changes then:

Then if write-to takes metadata location then we don't need to store compression codec on MetadataLocation at all (we can make it take a compression codec when generating the final path). (I actually need to double check this, there might be other places that try to reserialize the string).
We can eliminate a lot of the validation logic.

This is the place where we have to make a breaking change, so I think it's fine.

…pression

emkornfield · 2026-02-05T21:26:26Z

crates/iceberg/src/spec/table_properties.rs

+
+    #[test]
+    fn test_parse_metadata_file_compression_valid() {
+        use super::parse_metadata_file_compression;


need to move these imports out and clean up this code a little bit.

emkornfield · 2026-02-10T23:22:34Z

@blackmwk thanks for the review, I believe I addressed comments.

emkornfield · 2026-02-26T22:57:32Z

@blackmwk just wanted to ping on this? Thank you for your time.

emkornfield added 12 commits November 13, 2025 00:45

feat!: Support compression codecs for JSON metadata and Avro

665b970

Previously these properties where not honored on tabel properties. - Adds table properties for these values. - Plumbs them through for writers.

fmt

091d3bc

fix clippy

41a8c1c

clippy again

51e781e

wip

253bf59

address comments

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no clone needed

9d27116

test compression works

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comments

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update tests

46fdb8e

address comments

ec96917

Remove Avro compression changes, keep only JSON metadata compression

46efa9e

liurenjie1024 reviewed Nov 20, 2025

View reviewed changes

emkornfield added 9 commits November 20, 2025 18:19

address some comments

e96fe1a

don't reference deprecated method

53d0997

don't call deprecated method

4f033e8

with_next_version

2db8b89

refactor

8b63161

fix imports

9308050

fix compile

9bd46d6

fix clipp

f3276ce

remove ;

27cbc0b

emkornfield commented Nov 21, 2025

View reviewed changes

crates/catalog/s3tables/src/catalog.rs Show resolved Hide resolved

kevinjqliu approved these changes Nov 21, 2025

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liurenjie1024 reviewed Nov 21, 2025

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emkornfield and others added 4 commits November 21, 2025 08:54

Update crates/iceberg/src/spec/table_properties.rs

bdc6bb5

Co-authored-by: Kevin Liu <kevinjqliu@users.noreply.github.com>

address comment on .gz

05fdd81

Merge branch 'feat/metadata-compression' of github.com-personal:emkor…

5d6404c

…nfield/iceberg-rust into feat/metadata-compression

add tests

207c0bf

emkornfield requested a review from liurenjie1024 January 21, 2026 06:03

emkornfield mentioned this pull request Jan 29, 2026

feat: Factor out CompressionCodec to common location and add Gzip #2081

Merged

emkornfield added 7 commits January 29, 2026 03:49

Merge remote-tracking branch 'databricks/main' into feat/metadata-com…

1bfa1b8

…pression

wip

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fix

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cleanup

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wip

e17b626

fmt

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Clippy

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blackmwk reviewed Feb 2, 2026

View reviewed changes

emkornfield requested a review from blackmwk February 2, 2026 04:12

emkornfield mentioned this pull request Feb 2, 2026

feat!: Support compression codecs for Avro Files (including manifest and manifest lists) #1851

Draft

emkornfield added 4 commits February 5, 2026 18:56

wip

fa7f1a9

use CompressionCodec on metadata location

f2595df

change write_to

24ccd8f

Merge remote-tracking branch 'databricks/main' into feat/metadata-com…

0bf562b

…pression

emkornfield commented Feb 5, 2026

View reviewed changes

emkornfield added 6 commits February 5, 2026 21:33

fix nits

ab8a4b5

fix s3tables compilation

91df534

address comments

19209ce

fix compilation

3588283

fmt

bd54626

fix

e1d8d0b

emkornfield added 2 commits February 12, 2026 00:12

Merge branch 'main' into feat/metadata-compression

8aa2df6

Merge branch 'main' into feat/metadata-compression

391ee56

	/// Only used for creating a new table. For updates, see `with_next_version`.
	/// Only used for creating a new table. For updates, see `with_next_version_and_properties`.

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