pin nightly rustc version in release ci job

.github/workflows/roapi_http_release.yml

@@ -89,7 +89,7 @@ jobs:
       - name: Install Rust toolchain
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2021-07-17
           target: ${{ matrix.platform.target }}
           profile: minimal
           default: true
@@ -127,8 +127,10 @@ jobs:
       - name: Install Rust toolchain
         run: |
           rustup update nightly
-          rustup target add --toolchain nightly ${{ matrix.platform.target }}
-          rustup default nightly
+          rustup target add \
+            --toolchain nightly-2021-07-17 \
+            ${{ matrix.platform.target }}
+          rustup default nightly-2021-07-17
       - name: Build Wheels
         run: |
           pip3 install 'maturin<0.12'

columnq-cli/README.md

@@ -20,3 +20,11 @@ columnq(sql)> show columns from uk_cities;
 | datafusion    | public       | uk_cities  | lng         | Float64   | NO          |
 +---------------+--------------+------------+-------------+-----------+-------------+
 ```
+
+The Columnq CLI can also be used as a handy utility to Convert tabular data
+between various formats: `json`, `parquet`, `csv`, `yaml`, `arrow`, etc.
+
+```
+columnq sql --table 't:test_data/uk_cities_with_headers.csv' 'SELECT * FROM t' --output json
+cat test_data/blogs.parquet | columnq sql --table 't:stdin,format=parquet' 'SELECT * FROM t' --output json
+```