# Memory Group By The Memory Group By step groups rows in memory from a source step. The resulting rows are grouped based on a specified field or collection of fields. A new row is generated for each group. This step differs from the [Group By](https://github.com/pentaho/documentation/blob/main/PDIA/10.2/PDI/Transformation%20steps/PDI%20transformation%20steps%20reference%20\(overview\)/Group%20By%20-%20landing%20page%20article=GUID-A08851B3-A78C-4416-BF7E-052B32B949AF=3=en=.md) step by processing all rows in memory, and is designed to handle non-sorted input. If the number of rows you want to group is too large to fit into memory, you must use a combination of the [Sort rows](/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/sort-rows-transformation-step.md) and Group By steps. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.pentaho.com/pdia-data-integration/10.2-data-integration/pdi-transformation-steps-reference-overview/memory-group-by.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.