37 lines
2.4 KiB
Markdown
37 lines
2.4 KiB
Markdown
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# Query Engine Glossary
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This is a short glossary for the query-engine and IR discussion.
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## Terms
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- `IR`: Intermediate representation. A simpler form that sits between elaboration and execution.
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- `lowering`: The step that converts elaborated Geolog code into the IR.
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- `table`: A relational object in the IR. It describes stored data with columns and sometimes a primary key.
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- `law`: A logical rule or constraint in the IR. It says what relationships must hold about the data.
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- `law checking`: Testing whether the current data satisfies a law.
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- `query engine`: The execution component that consumes the IR and answers queries. In a broader design it may also do law checking, chase steps, and
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fixpoint work.
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- `backend`: A concrete execution target, such as an in-memory database, Postgres, or a Rust-native storage/query layer.
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- `backend-neutral`: Not tied to one storage or execution technology. The IR should ideally be backend-neutral.
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- `RelTable`: A table representing a relation or predicate.
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- `FunTable`: A table representing something function-like, where input columns determine an output.
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- `foreignKeys`: Generated laws saying that if one row exists, dependent rows must also exist.
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- `total`: Generated laws saying that if the inputs to a function exist, an output row must exist too.
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- `runtime IR`: A second execution-oriented representation above the lowered theory IR. It would hold changing state needed during execution.
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- `runtime state`: Mutable or evolving execution data, such as current facts, branch identity, witness allocation, equality classes, or provenance.
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- `fixpoint`: The point where running the rules produces no new facts or changes.
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- `chase`: The general reasoning process that repeatedly checks laws and adds whatever is needed to satisfy them.
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- `witness`: A fresh element introduced to satisfy an existential conclusion.
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- `branch`: One possible world or execution path created by a disjunctive rule.
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- `equality merging`: Collapsing two terms or elements when the theory says they must be equal.
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- `provenance`: Information about where a fact came from or which rules produced it.
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- `planning`: Choosing how to execute a query or check a law efficiently.
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- `adapter`: A layer that maps shared IR execution concepts onto one specific backend.
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## Short mental model
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- the front end parses, elaborates, and lowers
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- the IR is the contract
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- the query engine consumes that contract
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- the backend is where execution actually lands
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