# Considerations and limitations
<a name="column-stats-notes"></a>

The following considerations and limitations apply to generating column statistics.

**Considerations**
+ Using sampling to generate statistics reduces run time, but can generate inaccurate statistics.
+ Data Catalog doesn't store different versions of the statistics.
+ You can only run one statistics generation task at a time per table.
+ If a table is encrypted using customer Amazon KMS key registered with Data Catalog, Amazon Glue uses the same key to encrypt statistics.

**Column statistics task supports generating statistics:**
+ When the IAM role has full table permissions (IAM or Lake Formation).
+ When the IAM role has permissions on the table using Lake Formation hybrid access mode.

**Column statistics task doesn’t support generating statistics for:**
+ Tables with Lake Formation cell-based access control
+ Transactional data lakes - Linux foundation Delta Lake, Apache Hudi
+ Tables in federated databases - Hive metastore, Amazon Redshift datashares
+ Nested columns, arrays, and struct data types.
+ Table that is shared with you from another account