Skip flattening for mutations across imports

[vish-cs]

We currently flatten mutations across all imports and write to spanner. This PR processes each import independently to avoid any cross-dependency.
Updated wait signals for spanner writes to perform node writes without waiting for edge/obs deletions to complete.
Added import name to all the dataflow steps for easier debugging.
Also, remove edge generation for dcid property.

[gemini-code-assist]

Summary of Changes

Hello @vish-cs, 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 significantly refactors the graph ingestion pipeline by changing how mutations are handled. Instead of aggregating all mutations from various imports and then flattening them for a single write operation, the pipeline now processes and writes mutations for each import individually. This change streamlines the data flow, improves the correctness of dependency handling between delete and write operations, and enhances the clarity of the ingestion process by isolating mutation handling per import.

Highlights

• Refactored Mutation Processing: The pipeline now processes and writes mutations for each import independently, eliminating the previous approach of collecting and flattening all mutations across multiple imports before writing.
• Streamlined Dependency Management: Delete operations and subsequent writes for nodes, edges, and observations are now chained directly within the processing of each individual import, ensuring correct order and dependencies.
• Improved GraphReader Logic: The GraphReader was updated to explicitly skip 'dcid' properties when generating edges, preventing potential incorrect edge creation.
• Simplified Integration Tests: Integration tests were adjusted to reflect the per-import processing, removing the need for dynamically generated import names.

Changelog

• pipeline/ingestion/src/main/java/org/datacommons/ingestion/pipeline/GraphIngestionPipeline.java
  • Removed global lists for collecting mutations (delete, observation, node, edge) from buildPipeline.
  • Modified the processImport method signature to remove parameters for mutation collection lists.
  • Implemented per-import delete operations for observations and edges, introducing PCollection<Void> signals (deleteObsWait, deleteEdgesWait) for dependency management.
  • Integrated direct calls to spannerClient.writeMutations within the processImport loop for nodes, edges, and observations, ensuring mutations are written per import and respect dependencies.
  • Updated GraphReader.graphToNodes and GraphReader.graphToEdges calls to include an importName prefix for better identification in the pipeline.
  • Corrected a typo in a variable name from deleteObsWaitt to deleteObsWait.
• pipeline/ingestion/src/test/java/org/datacommons/ingestion/pipeline/GraphIngestionPipelineIntegrationTest.java
  • Removed the java.util.UUID import.
  • Changed the importName initialization from a UUID-generated string to a static 'TestImport' string.
• pipeline/util/src/main/java/org/datacommons/ingestion/util/GraphReader.java
  • Removed java.util.Arrays and org.apache.beam.sdk.Pipeline imports.
  • Added a check in graphToEdges to skip the 'dcid' property when iterating through node properties to prevent incorrect edge generation.
  • Removed the deleteExistingDataForImport helper method, as its functionality was moved to GraphIngestionPipeline.java.
• pipeline/util/src/test/java/org/datacommons/ingestion/util/GraphReaderTest.java
  • Added a 'dcid' property to a test graph node in testGraphToEdges to validate the new dcid skipping logic.

Activity

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[gemini-code-assist]

Code Review

This pull request refactors the ingestion pipeline to process each import individually, which is a good architectural improvement for scalability. However, the current implementation introduces a few issues. I've identified a typo that will cause a compilation failure, a null pointer exception when deletes are skipped due to incorrect initialization of wait signals, and a potential data consistency issue where node writes no longer wait for deletions. My review includes specific code suggestions to address these critical and high-severity problems.

[n-h-diaz]

nit: maybe update since it isn't flattening anymore?