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Repository Structure & Module Organization

Databend is a Rust workspace rooted at Cargo.toml. Start by deciding whether the change belongs to the query engine or the metadata system, then read the closest module README before editing.

Start Here: Meta vs Query

  • src/query/ is the main query engine: SQL parsing, planning, optimization, expression evaluation, execution pipeline, query service integration, and table/storage-facing behavior all converge here. If the task changes SQL behavior, planner output, execution, storage access, or query-side tests, start with src/query/README.md.
  • src/meta/ is the metadata side of the system: metadata types, protocol definitions, compatibility layers, supporting tooling, and the Databend meta-service binaries live here. If the task touches catalog/schema metadata, protobuf compatibility, meta APIs, or databend-meta tooling, start with src/meta/README.md.
  • src/meta/README.md also notes an important boundary: core meta-service implementation has moved to the separate databend-meta repository. Read it early if you suspect the code you need is no longer in this workspace.

Query Module Guide

  • Use src/query/README.md as the index for query-side crates. It explains the role of modules such as ast, catalog, expression, functions, pipeline, service, storages, and related support crates.
  • Prefer the nearest module README when one exists instead of inferring structure from directory names alone.
  • Read src/query/ast/README.md when the task is about SQL parser structure, grammar internals, or parser-specific development workflow.
  • Read src/query/functions/README.md when adding or debugging scalar or aggregate functions, function registration, or function-specific tests.
  • Read src/query/ee_features/README.md when the task involves enterprise query features and you need to confirm which feature layer owns the behavior.
  • Read src/query/sql/README.md when the task lives in SQL planning, binding, optimizer behavior, or SQL-side planner tests.

Other Workspace Landmarks

  • Shared crates live in src/common/.
  • Binaries are stored under src/binaries/.
  • Tests live in tests/, including SQL suites under tests/suites/, sqllogic cases, and meta-specific harnesses.
  • Performance experiments live in benchmark/.
  • Tooling and deployment helpers live in scripts/ and docker/.
  • Fixtures live in _data/.
  • The Makefile lists supported top-level tasks.