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Short Description

Waiting for a read from a relation data file.

Additional Information

DataFileRead is an IO wait event and indicates that a process is currently waiting for data to be read from disk or the page cache.

How to reduce this wait

If you frequently see this wait event then you might want to examine the SQL statements which cause the most I/O and look for optimizations.

  • Can you accomplish the same result while examining less data?
  • If not, is there an index that might make the processing more efficient?
  • Can the SQL be restructured to generate a more optimal plan?
  • If no application-level optimisations are possible, then can the I/O subsystem be optimised somehow?

PostgreSQL documentation - The Statistics Collector - Tuning Input/Output (I/O) Operations for PostgreSQL

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