When pyiceberg loads Iceberg tables data into memory, dictionary encoding is not applied for columns

[learningkeeda]

Apache Iceberg version

0.7.0

Please describe the bug 🐞

When I try to load large dataset as below, string columns data is stored in its original, uncompressed form, leading to increased memory usage which leads to out-of-memory errors.

from pyiceberg.catalog import load_catalog
from pyiceberg.expressions import GreaterThanOrEqual

catalog = load_catalog("default")
table = catalog.load_table("test.table1")
table.scan(
selected_fields=("id", "string_cols1", "string_cols2"),
).to_arrow()

To avoid these issues, it's best to use dictionary encoding, especially for columns with low cardinality, where values are repeated frequently.