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GlueSQL

  • Type: Open-source contribution
  • Period: Jun 2021 - Present

Implementing DISTINCT Execution Semantics

Problem and diagnosis: SELECT DISTINCT syntax information did not reach GlueSQL's Rust SQL engine executor, so the query produced the same result as a regular SELECT. Projection and aggregate execution identify duplicates at different state boundaries.

Constraints and decision: I preserved non-DISTINCT behavior and split deduplication by execution path: SELECT DISTINCT deduplicates projected result rows, while aggregate DISTINCT deduplicates the values supplied to each aggregate function. Unsupported DISTINCT ON returns an explicit error.

Scroll horizontally to inspect the full flow.

DISTINCT syntax moves through the parser and AST into the query model, then the execution path deduplicates projected rows or aggregate inputs before regression tests verify the behavior.

Implementation: I propagated parser/AST output into the query model, then connected row deduplication and aggregate handling in the SQL executor with AST Builder APIs. Consistent deduplication required equal values to produce the same hash and equivalent maps to compare equally regardless of key insertion order. I updated value comparison, hashing, and map-key ordering together to preserve those invariants.

Validation and result: Regression tests covered single and multiple columns, maps, schemaless rows, and aggregate DISTINCT, including COUNT. The feature and tests preserve the same meaning across SQL input, internal representation, and execution output.

Additional Work

  • Parser dependency evaluation: I assessed an in-house parser against the compatibility cost of the public AST and Query Builder. In the same copy of core, the sqlparser check took 2.6 seconds with only sqlparser/serde disabled and 8.0 seconds after re-enabling it; the baseline and feature-disabled configurations each passed 593 core tests. I kept bigdecimal because the AST conversion depends on it and chose PR #2042 to remove only unused serde. Consumers serializing the public AST may need to enable the feature directly.
  • AST Query Interface: I implemented AST Builder aggregate helpers and COUNT argument handling, then updated the executor and tests to evaluate expression arguments.
  • Parquet Storage and CLI: I connected Parquet to the storage traits and SQL execution, adding file read/write, schema and value conversion, documentation, tests, and a CLI usage path. I later updated the code to meet clippy::pedantic checks.

Review and Mentoring

As of July 10, 2026, I had authored 50 merged pull requests in gluesql/gluesql. I now participate in code review and maintenance as a GlueSQL reviewer, reviewing contributor pull requests for error handling, edge cases, test coverage, and code organization. As an OSSCA mentor in 2023, I guided contributors through Rust project workflows, GlueSQL internals, storage, AST Builder, and function implementation.

The GlueSQL team I joined received the Open Source Contribution Academy's NIPA President Award (Top Excellence) in 2021 and 2022. The GlueSQL team I mentored received a NIPA Encouragement Award in 2023.