Remove classic pagination

[AntonKhorev]

This removes classic pagination library that's only used for changeset elements pagination:

• necessary parts of its Paginator class moved to controller's ElementsPaginator
• necessary parts of PaginationHelper module moved to sidebar_classic_pagination helper

[tomhughes]

Shouldn't we just be converting changesets to use the same pagination logic as everything else, rather than copying parts of classic pagination into the controller just so we can pretend we got rid of it?

[AntonKhorev]

Shouldn't we just be converting changesets to use the same pagination logic as everything else

That depends on how significant are the differences between changeset elements and everything else. The differences are:

• Changesets have an upper bound on the number of elements. There can be a really large and growing number of traces etc. If you wanted to use numbered pages and go to page N, that N could be huge and you'll have to skip a huge number of record with offset. But for changeset elements N can't get higher than 10000 / page size.
• Changesets don't change once closed. For a list of traces it doesn't make mach sense to be on page 1, 2, 5 etc because new traces are added and old ones are pushed off the page. Changeset elements are not going to be pushed of their page.
• Traces etc have a well-defined order represented by a single id, changeset elements don't.

[gravitystorm]

Shouldn't we just be converting changesets to use the same pagination logic as everything else, rather than copying parts of classic pagination into the controller just so we can pretend we got rid of it?

I agree.

• Changesets have an upper bound on the number of elements. There can be a really large and growing number of traces etc. If you wanted to use numbered pages and go to page N, that N could be huge and you'll have to skip a huge number of record with offset. But for changeset elements N can't get higher than 10000 / page size.

• Changesets don't change once closed. For a list of traces it doesn't make mach sense to be on page 1, 2, 5 etc because new traces are added and old ones are pushed off the page. Changeset elements are not going to be pushed of their page.

These are good reasons why the paginator doesn't have to be cursor-based, but they aren't reasons why it can't be cursor-based. So I think the simplification of only having one type of pagination is worthwhile.

• Traces etc have a well-defined order represented by a single id, changeset elements don't.

Since we need a well-defined order for either approach to work, I think it's best to get the order defined and working with the cursor-based pagination.

[AntonKhorev]

These are good reasons why the paginator doesn't have to be cursor-based, but they aren't reasons why it can't be cursor-based. So I think the simplification of only having one type of pagination is worthwhile.

Do you propose to remove the ability to go to page N?

[gravitystorm]

Do you propose to remove the ability to go to page N?

Sure, I don't see a strong need for that. Particularly if the order hasn't been defined before.

[AntonKhorev]

Do you also propose to remove the ability to see how many elements of each type were changed?

[gravitystorm]

No.

[AntonKhorev]

These are good reasons why the paginator doesn't have to be cursor-based, but they aren't reasons why it can't be cursor-based. So I think the simplification of only having one type of pagination is worthwhile.

Those were reasons for why this place is different, why it might be feasible not to downgrade the pagination here and why there won't necessarily be any simplification even if we downgrade it.

Since we need a well-defined order for either approach to work, I think it's best to get the order defined and working with the cursor-based pagination.

Do you want to introduce a single id or or some other field (like relation elements have) and sort by it?

[github-actions]

	1 Warning
⚠️	Number of updated lines of code is too large to be in one PR. Perhaps it should be separated into two or more?

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