Some ODBC drivers support a customizable buffer size, for which you can specify the number of rows or amount of memory to allocate for batches of results. The driver uses the buffer to return results to Tableau. Slow performance usually means that the value is too small, and Tableau needs to send frequent queries to the database, increasing the time it takes to populate a view or create an extract.
When you set this value, you want to find the right balance between frequency of queries to the database and amount of memory required for each fetch operation. If you set the value too large, you will experience memory allocation or out of memory errors.
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