On Tue, Jul 08, 2025 at 09:31:29PM +0300, Nikita Malakhov wrote: > Michael, one more thing forgot to mention yesterday - > #define TOAST_EXTERNAL_INFO_SIZE (VARTAG_ONDISK_OID + 1) > static const toast_external_info > toast_external_infos[TOAST_EXTERNAL_INFO_SIZE] > VARTAG_ONDISK_OID historically has a value of 18 > and here we got an array of 19 members with only 2 valid ones.
Yeah, I'm aware of that. The code is mostly to make it easier to read while dealing with this historical behavior, even if it costs a bit more in memory. I don't think that it's a big deal, and we could always have one more level of redirection to reduce its size. Now there's the extra complexity.. > What do you think about having an individual > TOAST value id counter per relation instead of using > a common one? I think this is a very promising approach, > but a decision must be made where it should be stored. I've thought about that, and decided to discard this idea for now to keep the whole proposal simpler. This has benefits if you have many relations with few OIDs consumed, but this has a cost in itself as you need to maintain the data for each TOAST relation. When I looked at the problems a couple of weeks ago, I came to the conclusion that all the checkbox properties of "local" TOAST values are filled with a sequence: WAL logging to ensure uniqueness, etc. So I was even considering the addition of some code to create sequences on-the-fly, but at the end that was just more complexity with how we define sequences currently compared to a unique 8-byte counter in the control file that's good enough for a veeery long time. I've also noticed that this sort of links to a piece I've implemented last year and is still sitting in the CF app without much interest from others: sequence AMs. You could implement a "TOAST" sequence method, for example, optimized for this purpose. As a whole, I propose to limit the scope of the proposal to the pluggability of the external TOAST pointers. The approach I've taken should allow such improvements, these can be added later if really needed. -- Michael
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