Parameter values contain data types that cannot be serialized in the multi-row INSERT format. A NULL value in a batch row causes the rewrite to fail if the column is not nullable. Very large batch sizes exceeding the connector's internal rewrite limit. Mixing Python types that map to incompatible Snowflake column types in the same batch. Using executemany() with a format string that includes non-standard placeholders

Reduce the batch size: split large executemany() calls into smaller batches (e.g., 1000 rows at a time).. Check for NULL values in non-nullable columns and filter them before insertion.. Ensure all rows in the batch have the same Python data types for each column.. Disable the multi-row rewrite optimization if it causes issues: cursor.execute() with individual rows instead of executemany().. Use the Snowflake bulk loading (COPY INTO) approach for large inserts instead of executemany().

Medium severityexecutionSnowflake →

Power BI Refresh Error:
252001

What does this error mean?

The Python connector attempted to optimize a batch INSERT by rewriting multiple single-row inserts into a multi-row statement, but the rewrite failed. This is an internal connector optimization that can fail due to data formatting or parameter binding issues.

Common causes

1Parameter values contain data types that cannot be serialized in the multi-row INSERT format
2A NULL value in a batch row causes the rewrite to fail if the column is not nullable
3Very large batch sizes exceeding the connector's internal rewrite limit
4Mixing Python types that map to incompatible Snowflake column types in the same batch
5Using executemany() with a format string that includes non-standard placeholders

How to fix it

1Reduce the batch size: split large executemany() calls into smaller batches (e.g., 1000 rows at a time).
2Check for NULL values in non-nullable columns and filter them before insertion.
3Ensure all rows in the batch have the same Python data types for each column.
4Disable the multi-row rewrite optimization if it causes issues: cursor.execute() with individual rows instead of executemany().
5Use the Snowflake bulk loading (COPY INTO) approach for large inserts instead of executemany().

Frequently asked questions

Is COPY INTO better than executemany() for large inserts?

Yes for bulk loads — COPY INTO is significantly faster for thousands of rows or more. Use executemany() for small incremental inserts (under a few hundred rows).

How do I know the rewrite is happening?

Enable connector logging (logging.basicConfig(level=logging.DEBUG)) and look for messages about multi-row rewrite attempts.

Official documentation: https://github.com/snowflakedb/snowflake-connector-python/blob/main/src/snowflake/connector/errorcode.py