On Sun, Feb 14, 2021 at 7:56 PM Michael Paquier <michael@paquier.xyz> wrote:
On Sun, Feb 14, 2021 at 09:29:08AM +0800, Andy Fan wrote: > Thank you tom for the reply. What would be the difference between the > SPI and "write a pure SQL UDF" and call it with DirectFunctionCall1? I > just ran into a similar situation some days before. Currently I think > DirectFunctionCall1 doesn't need to maintain a connection but SPI has to > do that.
Hard to say without knowing your use case. A PL function is more simple to maintain than a C function, though usually less performant from the pure point of view of its operations. A SQL function could finish by being inlined, allowing the planner to apply optimizations as it would know the function body. Going with SPI has the advantage to have code able to work without any changes across major versions, which is a no-brainer when it comes to long-term maintenance. -- Michael