[BigQueryIO] Improve sharding for bounded pcolleciton

[stankiewicz]

Improve sharding for bounded pcolleciton, to better control concurrent connections. this will keep elements for same destination close to each other and shard them. For single table write it's same behaviour, for dynamic destination it will improve reduce amount of connections used.

this is batch only change, streaming improvement will need some thinking, as this is breaking change.

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[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request optimizes sharding behavior for bounded PCollections within the BigQuery Storage API write path. By introducing a key-based redistribution strategy for bounded inputs, it ensures that data destined for the same table is grouped effectively, which improves connection efficiency and resource utilization when writing to dynamic destinations.

Highlights

• Improved Sharding Logic: Implemented a specific sharding strategy for bounded PCollections in BigQueryIO to better manage concurrent connections.
• Deterministic Hashing: Utilized Murmur3 hashing on table URNs to ensure elements for the same destination are grouped together, reducing connection overhead for dynamic destinations.

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[gemini-code-assist]

Code Review

This pull request updates the sharding logic in StorageApiLoads.java to handle bounded and unbounded PCollections differently when numShards is specified. For bounded collections, it introduces a custom sharding mechanism based on the hash of the destination table's URN. The review feedback points out a critical bug where using Math.abs with modulo can result in a negative shard index if the value is Integer.MIN_VALUE, and suggests using Math.floorMod instead to ensure a non-negative shard index.

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[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates StorageApiLoads to handle sharding differently for bounded and unbounded inputs when numShards > 0. For bounded inputs, it applies a custom sharding key based on the table URN hash and a random integer before redistributing. However, using WithKeys.of to call dynamicDestinations.getTable(...) can fail at runtime if the implementation relies on side inputs. It is recommended to use a custom DoFn with ParDo to properly support side inputs.

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[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates StorageApiLoads to handle sharding differently for bounded and unbounded PCollections when numShards > 0. For bounded inputs, it introduces a new AddShardKeyFn to assign shard keys based on the table URN hash and a random factor, redistributes by key, and then removes the shard key. The feedback points out that AddShardKeyFn must be declared as a static inner class to prevent serialization issues at runtime, as non-static inner classes maintain an implicit reference to their enclosing class.

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[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request updates StorageApiLoads.java to handle sharding differently for bounded and unbounded inputs. For bounded inputs, it introduces a new AddShardKeyFn to assign shard keys before redistributing. Feedback on this implementation points out that AddShardKeyFn should be static to avoid serialization issues, and that its sharding logic should use a per-bundle random offset rather than a per-element random number to properly group elements by destination.

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[stankiewicz]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces sharding for bounded inputs in 'StorageApiLoads' when 'numShards > 0' by adding a new 'AddShardKeyFn' to assign shard keys. The review feedback highlights two critical issues in 'AddShardKeyFn': first, using XOR with 'ThreadLocalRandom' leads to non-uniform shard distribution when 'numShards' is not a power of two; second, keying solely by the shard key interleaves multiple destinations, causing connection thrashing downstream. The reviewer recommends using addition instead of XOR and a composite key 'KV<DestT, Integer>' to ensure uniform distribution and efficient connection management.

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[github-actions]

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R: @chamikaramj for label java.

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