Add ADBC reader behind 'adbc' feature

.github/workflows/build.yaml

@@ -32,6 +32,11 @@ jobs:
       - name: Install LLVM
         run: sudo apt-get install -y llvm
 
+      - name: Install protobuf compiler
+        # adbc_datafusion (dev-dep) → datafusion → substrait → prost-build,
+        # which invokes `protoc` at build time. Required for the ADBC test path.
+        run: sudo apt-get install -y protobuf-compiler
+
       - name: Install Rust
         uses: dtolnay/rust-toolchain@stable
 
@@ -61,6 +66,17 @@ jobs:
       - name: Run Rust tests
         run: cargo test --lib --bins
 
+      - name: Install dbc CLI and SQLite ADBC driver
+        run: |
+          curl -LsSf https://dbc.columnar.tech/install.sh | sh
+          "$HOME/.local/bin/dbc" install sqlite
+
+      - name: Run ADBC unit tests
+        run: cargo test --features "adbc sqlite" --lib
+
+      - name: Run ADBC SQLite equivalence tests
+        run: cargo test --features "adbc sqlite" --lib -- --ignored equivalence
+
       - name: Build WASM library
         working-directory: ggsql-wasm/library
         run: npm install && npm run build

CHANGELOG.md

@@ -1,7 +1,12 @@
 ## [Unreleased]
 
 ### Added
-
+- New `AdbcReader<D: Driver>` for connecting to data sources via
+  [ADBC](https://arrow.apache.org/adbc/) (Arrow Database Connectivity), behind
+  a new off-by-default `adbc` feature flag. Generic over any concrete
+  `adbc_core::sync::Driver`, so concrete drivers (Flight SQL, Snowflake, etc.)
+  compose at the call site. Tested against `adbc_datafusion` for in-process
+  unit coverage.
 - New `aggregate` SETTING on Identity-stat layers (point, line, area, bar, ribbon,
   range, segment, arrow, rule, text). By default it collapses each group to a
   single row by replacing every numeric mapping in place with its aggregated