Configuration

The Builder API gives fine-grained control over how FlowLog compiles your Datalog programs. Use it in build.rs when the one-liner compile() isn't enough.

Builder API

fn main() {
    flowlog_build::Builder::default()
        .sip(true)                                   // Sideways Information Passing
        .string_intern(true)                         // String interning
        .mode(flowlog_build::ExecutionMode::DatalogIncremental) // Incremental mode
        .profile(true)                               // Operator profiling
        .udf_file("udfs.rs")                         // User-defined functions
        .compile(
            &["program.dl"],                         // Program files
            &["include/"],                           // Include directories
        )
        .unwrap();
}

Options reference

Method	Type	Default	Description
mode(m)	ExecutionMode	DatalogBatch	Execution mode: DatalogBatch or DatalogIncremental.
sip(flag)	bool	false	Enable Sideways Information Passing for demand-driven evaluation.
string_intern(flag)	bool	false	Intern string values for reduced memory and faster equality checks.
profile(flag)	bool	false	Emit per-operator profiling counters in the generated code.
udf_file(path)	impl AsRef<Path>	none	Path to a Rust source file containing user-defined functions.

compile(programs, includes)

The terminal method. Accepts:

• programs — a slice of .dl file paths to compile.
• includes — a slice of directories to search for .include directives.

Returns Result<(), BoxError>.

Execution mode

Mode	Enum variant	When to use
Batch	ExecutionMode::DatalogBatch	Load all data, compute once, read results.
Incremental	ExecutionMode::DatalogIncremental	Stream updates over time, observe deltas per epoch.

Batch mode generates a DatalogBatchEngine with insert_* and run() methods. Incremental mode generates a DatalogIncrementalEngine with begin(), put_*(), file_*(), and commit() for transactional updates.

Runtime crate

The flowlog-runtime crate provides types used by the generated code:

• Relation trait — auto-implemented on every generated relation type, providing relation_name() and to_tuple().
• intern module — thread-safe string interning (used when string_intern is enabled).
• io module — CSV file reader and parallel data ingestion helpers.
• txn module — transaction primitives for incremental mode (Diff, TxnOp, TxnAction, TxnState).

Error handling

Builder::compile returns a Result. Common failure modes:

• Parse errors in the .dl file — the error message includes line and column.
• Missing UDF file — the path passed to udf_file() does not exist.
• Type mismatches — UDF signatures don't match their .extern fn declarations.

fn main() {
    if let Err(e) = flowlog_build::Builder::default()
        .compile(&["program.dl"], &[])
    {
        eprintln!("FlowLog build failed: {e}");
        std::process::exit(1);
    }
}