Differential Dataflow Backend

Cargo.toml

@@ -5,13 +5,15 @@ members = [
   "egglog/concurrency",
   "egglog/core-relations",
   "egglog/egglog-ast",
+  "egglog/egglog-backend-trait",
   "egglog/egglog-bridge",
   "egglog/egglog-reports",
   "egglog/numeric-id",
   "egglog/union-find",
   "egglog/src/sort/add_primitive",
   "egglog/wasm-example",
   "egglog-experimental",
+  "egglog-experimental/flowlog",
 ]
 
 [workspace.package]
@@ -81,6 +83,7 @@ egglog-numeric-id = { path = "egglog/numeric-id", version = "2.0.0" }
 egglog-union-find = { path = "egglog/union-find", version = "2.0.0" }
 egglog-add-primitive = { path = "egglog/src/sort/add_primitive", version = "2.0.0" }
 egglog-reports = { path = "egglog/egglog-reports", version = "2.0.0" }
+egglog-backend-trait = { path = "egglog/egglog-backend-trait", version = "2.0.0" }
 egglog = { path = "egglog", default-features = false, version = "2.0.0" }
 
 ######################
@@ -89,6 +92,14 @@ egglog = { path = "egglog", default-features = false, version = "2.0.0" }
 wasm-bindgen = "0.2"
 
 
+# The FlowLog backend (egglog-experimental/flowlog) uses a `differential-dogs3`
+# (dogsdogsdogs) that path-deps its own differential-dataflow; redirect the
+# crates.io differential-dataflow to the same git source so the workspace shares
+# a single dd 0.24.0. Only FlowLog pulls these in. A `[patch]` is only honored at
+# the workspace root, so it lives here rather than in the FlowLog crate.
+[patch.crates-io]
+differential-dataflow = { git = "https://github.com/oflatt/differential-dataflow", rev = "f8d47afb6996942358d36f0ca5796412caf3fe94" }
+
 [profile.dev]
 opt-level = 3
 debug = "line-tables-only"

egglog-experimental/flowlog/.gitignore

@@ -0,0 +1,2 @@
+/target
+/output.*.log

egglog-experimental/flowlog/Cargo.toml

@@ -0,0 +1,50 @@
+# A FlowLog (differential-dataflow) backend for egglog — it depends only on the
+# public `egglog-backend-trait` SPI plus the neutral `egglog-core-relations`.
+# This is the worked example that a third party can implement their own egglog
+# backend against the `Backend` trait.
+#
+# It stays on edition 2021 (its differential-dataflow / timely dependency tree is
+# edition 2021); the workspace `resolver = "3"` supports the mixed edition. The
+# `[patch.crates-io]` that pins differential-dataflow lives in the workspace-root
+# Cargo.toml (a patch is only honored there).
+[package]
+name = "egglog-experimental-flowlog"
+version = "0.1.0"
+edition = "2021"
+description = "A FlowLog (differential-dataflow)-backed egglog Backend, as an out-of-tree example of the egglog-backend-trait SPI."
+license = "MIT"
+publish = false
+
+[dependencies]
+anyhow = "1"
+egglog-backend-trait = { path = "../../egglog/egglog-backend-trait" }
+egglog-core-relations = { path = "../../egglog/core-relations" }
+egglog-numeric-id = { path = "../../egglog/numeric-id" }
+hashbrown = "0.16"
+log = "0.4"
+dyn-clone = "1.0.17"
+# Raw differential-dataflow + timely, used in-process by `dd_native.rs`.
+differential-dataflow = "=0.24.0"
+timely = "=0.30.0"
+# `--wcoj` worst-case-optimal join operators. `differential-dogs3` is the
+# crates.io name of `dogsdogsdogs`, which lives in the differential-dataflow
+# repo. We track the branch carrying the upstreamable `lookup_map` index-oob
+# fix (TimelyDataflow/differential-dataflow#765). Because that crate path-deps
+# the repo's own differential-dataflow, the `[patch]` below redirects our
+# crates.io differential-dataflow to the same source so there is a single dd.
+differential-dogs3 = { git = "https://github.com/oflatt/differential-dataflow", rev = "f8d47afb6996942358d36f0ca5796412caf3fe94" }
+serde = { version = "1", features = ["derive", "rc"] }
+
+[[test]]
+# Parity harness over egglog's .egg corpus: checks FlowLog's output against
+# egglog's OWN shared snapshots (`egglog/tests/snapshots/files__shared_snapshot_
+# *.snap`), so egglog is the single source of truth. Custom libtest-mimic main.
+name = "files"
+harness = false
+
+[dev-dependencies]
+# The frontend, so the integration tests can run real `.egg` files on the
+# FlowLog backend via `egglog::EGraph::with_backend(..)`.
+egglog = { path = "../../egglog", default-features = false }
+egglog-experimental = { path = "..", default-features = false }
+libtest-mimic = "0.8"