IO:DataFileExtend
DataFileExtend is a PostgreSQL wait event that occurs when a backend process is waiting for the physical extension of a data file (such as a table or index file) on disk.
This happens when a relation needs to grow—typically during INSERT, COPY, or index creation—and PostgreSQL must allocate and initialize new blocks in the file.
During extension, PostgreSQL usually writes zeros to the newly allocated portion of the file to ensure crash safety and prevent exposure of stale disk contents.
This I/O operation can block the backend until the file system confirms the allocation and initialization are complete.
DataFileExtend events may indicate:
- High data ingestion rates causing frequent file growth.
- Storage performance bottlenecks affecting file extension times.
- File system limitations impacting efficient file preallocation (e.g., missing fallocate or sparse file optimizations)