On 2019-11-06 18:00, Andres Freund wrote:
I'd like an AM to have the *option* of implementing something better, or at least go in the direction of making that possible.
I don't think the presented design prevents that. An AM can just return false from relation_needs_toast_table in all cases and implement something internally.
It seems perfectly possible to have a helper function implementing the current logic that you just can call with the fixed chunk size as an additional parameter. Which'd basically mean there's no meaningful difference in complexity compared to providing the chunk size as an external AM property. In one case you have a callback that just calls a helper function with one parameter, in the other you fill in a member of the struct.
I can see a "moral" concern about having TOAST be part of the table AM API. It should be an implementation concern of the AM. How much more work would it be to refactor TOAST into a separate API that an AM implementation could use or not? How much more complicated would the result be? I guess you would like to at least have it explored.
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