postgres-github.git / summary / log / commit / refs

commit    7f8c88c2b872cb74882ab93dcb05529dab2a10bc
Author:   Tomas Vondra <tomas.vondra@postgresql.org>
Date:     Thu Apr 02 10:53:18 2026 +0000

    jit: Change the default to off.
    
    While JIT can speed up large analytical queries, it can also cause
    serious performance issues on otherwise very fast queries. Compiling
    and optimizing the expressions may be so expensive, it completely
    outweighs the JIT benefits for shorter queries.
    
    Ideally, we'd address this in the cost model, but the part deciding
    whether to enable JIT for a query is rather simple, partially because we
    don't have any reliable estimates of how expensive the LLVM compilation
    and optimization is.
    
    Sometimes seemingly unrelated changes (for example a couple additional
    INSERTs into a table) increase the cost just enough to enable JIT,
    resulting in a performance cliff.
    
    Because of these risks, most large-scale deployments already disable JIT
    by default. Notably, this includes all hyperscalers.
    
    This commit changes our default to align with that established practice.
    If we improve the JIT (be it better costing or cheaper execution), we
    can consider enabling it by default again.
    
    Author: Jelte Fennema-Nio <postgres@jeltef.nl>
    Discussion: https://postgr.es/m/DG1VZJEX1AQH.2EH4OKGRUDB71@jeltef.nl

[parent: 148fe2b05df5]