Bedrock.DataPlane.Demux.MutationSlicer (bedrock v0.5.2)

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Slices a transaction's mutations by shard using the SHARD_INDEX section.

Given a transaction with mutations sorted by shard and a SHARD_INDEX section indicating how many mutations belong to each shard, this module produces per-shard "slices" - mini-transactions containing only that shard's mutations.

Slice Format

Each slice is a valid BRDT (transaction) binary containing:

  • Transaction header
  • MUTATIONS section with just that shard's mutations
  • COMMIT_VERSION section

This format allows materializers to decode slices using standard Transaction functions.

Summary

Types

shard_id()
slice()
version()

Functions

slice(transaction, commit_version)

Slices a transaction by shard, returning a list of {shard_id, slice} tuples.

slice!(transaction, commit_version)

Same as slice/2 but raises on error.

touched_shards(transaction)

Extracts shard IDs from a transaction without full slicing.

Types

shard_id()

@type shard_id() :: non_neg_integer()

slice()

@type slice() :: binary()

version()

@type version() :: Bedrock.version()

Functions

slice(transaction, commit_version)

@spec slice(binary(), binary()) :: {:ok, [{shard_id(), slice()}]} | {:error, term()}

Slices a transaction by shard, returning a list of {shard_id, slice} tuples.

The transaction must have a SHARD_INDEX section indicating how mutations are distributed across shards. Each slice is a valid transaction binary containing only the mutations for that shard.

Parameters

  • transaction - Encoded transaction binary with SHARD_INDEX
  • commit_version - The commit version to include in each slice (8-byte binary)

Returns

  • {:ok, [{shard_id, slice}]} - List of shard slices, one per shard touched
  • {:error, reason} - If transaction is invalid or missing SHARD_INDEX

Example

{:ok, slices} = MutationSlicer.slice(encoded_txn, commit_version)
# slices = [{0, slice_binary_0}, {2, slice_binary_2}, ...]

slice!(transaction, commit_version)

@spec slice!(binary(), binary()) :: [{shard_id(), slice()}]

Same as slice/2 but raises on error.

touched_shards(transaction)

@spec touched_shards(binary()) :: {:ok, [shard_id()]} | {:error, term()}

Extracts shard IDs from a transaction without full slicing.

Useful for determining which shards a transaction touches without creating the full slice binaries.

Returns

  • {:ok, [shard_id]} - List of shard IDs touched by the transaction
  • {:error, reason} - If SHARD_INDEX is missing or invalid