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https://github.com/qed-solver/prover

A SQL query equivalence prover in Rust aiming for high performance and wide SQL feature coverage.
https://github.com/qed-solver/prover

Last synced: 3 months ago
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A SQL query equivalence prover in Rust aiming for high performance and wide SQL feature coverage.

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README 

        
# The QED Prover



This is a SQL query equivalence prover in Rust aiming for high performance and wide SQL feature coverage.

The project starts as a successor of the Cosette prover, which is described in [this paper](https://www.vldb.org/pvldb/vol11/p1482-chu.pdf).



## Install



### Build from source manually



The project relies on a nightly Rust compiler toolchain,

and additionally, `libclang` and header files for `z3` are needed as build-time dependencies.

Build the prover with

```sh

cargo build --release

```

would produce an executable `./target/release/qed-prover`.

The current setup of the prover has the Z3 *and* CVC5 solver as a runtime dependency,

so you need to have both the `z3` *and* `cvc5` executable in the `PATH` when running `qed-solver`.



### Build with Nix



Alternatively, if one has Nix and Nix flake in their environment, this project contains a flake for easy reproducibility.

Simply use

```sh

nix run github:qed-solver/prover -- 

```

to run the prover with arguments ``.



To have a development environment with all the build-time and runtime dependencies, run `nix shell .` in the project's root.

For `direnv` users, a `.envrc` file is also prepared, so simply `cd` into the project directory, and `direnv` will try to reproduce the development environment.

(NOTICE: For first-time use, you need to explicitly trust the `.envrc` file, by executing `direnv allow .`)



## Usage



Normally, one invoke the parser as

```sh

qed-prover [input-path]...

```

where every `input-path` is a JSON file that represents a case to prove, or a directory containing such files.

Currently one can generate conforming JSON files using [this parser](https://github.com/qed-solver/parser) by passing in SQL statements.



During execution, the results will simply be printed out, with the names of every files followed by their result (provable/not provable).

One can use the environment variable `QED_SMT_TIMEOUT` to set a timeout for each SMT request the prover makes in milliseconds, which is defaulted to 10,000.

Setting the environment variable `RUST_LOG=info` when running would give a (very) verbose output.

This is useful for debugging as it prints out how expressions are simplified in the solver at various stages.



### Test cases



For convience, the directory `tests/calcite/` contains JSON files representing the query rewrite pairs use in the optimizer test suite of the [Calcite](https://calcite.apache.org/) project.

You may try out running these inputs by

```sh

qed-prover tests/calcite/

```

WARNING: some test cases in this folder contain features that we haven't support yet.

Now ~290 out of all ~440 cases are actually provable.



## Feature coverage



### Supported features



- Basic `SELECT-FROM-WHERE` queries

- Set operations (`UNION`, `UNION ALL`, `INTERSECT` (but not `INTERSECT ALL`), `EXCEPT`, and `EXCEPT ALL`)

- Joins (`INNER JOIN`, `LEFT`/`RIGHT`/`FULL` `OUTER JOIN`, `SEMI`/`ANTI` `JOIN`, and lateral/correlated join)

- `DISTINCT`

- `VALUES`

- Aggretation (as uninterpreted functions)

- `ORDER BY` and `LIMIT` (as uninterpreted operators)

- Value operations with subquery (`IN` and `EXISTS`)

- Unique key constraint

- Arbitrary `CHECK` constraints



### Planned features



- Foreign key constraint

- Law of excluded middle ($A + \neg A = 1$)



### Unsupported features



- Semantics of aggretations, such as understanding them as algebras over a monad

- Semantics of `ORDER BY` and `LIMIT` (requires temporarily modelling a table as list?)