test eager vs lazy in CI

.github/workflows/benchmark.yaml

@@ -35,6 +35,8 @@ jobs:
           cd tests/db-benchmark
           Rscript -e 'install.packages("data.table", repos="https://Rdatatable.github.io/data.table")'
           Rscript groupby-datagen.R 1e7 1e2 5 0
+          echo "LAZY vs EAGER tests"
+          python lazy_vs_eager.py
           echo "ON STRINGS"
           python main.py on_strings
           echo "ON CATEGORICALS"

py-polars/tests/db-benchmark/lazy_vs_eager.py

@@ -0,0 +1,9 @@
+import polars as pl
+
+path = "G1_1e7_1e2_5_0.csv"
+predicate = pl.col("v2") < 5
+
+shape_eager = pl.read_csv(path).filter(predicate).shape
+
+shape_lazy = (pl.scan_csv(path).filter(predicate)).collect().shape
+assert shape_lazy == shape_eager