perf(entgql): avoid COUNT(*) for pageInfo-only connection queries - #625

@a8m @giautm Please check this pull request for me 🙇‍♂️🙇‍♂️🙇‍♂️

@tutranngoc fyi, you can use entcache package to cache query result of count(). So it wont hit database twice.

https://github.com/ariga/entcache

@tutranngoc fyi, you can use entcache package to cache query result of count(). So it wont hit database twice.

https://github.com/ariga/entcache

@giautm Thank you for sharing, however, my preference is to eliminate the need for a select count when using pageInfo, even during the first query. Querying for count when using pageInfo is unnecessary.

I don't think this PR handles all edge cases for the pagination. If you create a query that looks like this:

variants(first: $firstVariant, after: $afterVariant) {
 pageInfo {
 hasNextPage
 endCursor
 }
 }

then we will not populate the pageInfo object correctly. If we request pagination info without any edges, we still need to do the count.

I solved the same problem using an external template, where I used this logic instead:

ignoredEdges := !hasCollectedField(ctx, edgesField)
needTotalCount := hasCollectedField(ctx, totalCountField)
needPageInfo := hasCollectedField(ctx, pageInfoField)
hasPagination := after != nil || first != nil || before != nil || last != nil
if (needTotalCount && hasPagination) || (ignoredEdges && (needTotalCount || needPageInfo)) {
	c := {{ $r }}.Clone()
	{{- /* Clear the selection fields before counting to avoid generating invalid queries. */}}
	c.ctx.Fields = nil
	if conn.TotalCount, err = c.Count(ctx); err != nil {
		return nil, err
	}
	conn.PageInfo.HasNextPage = first != nil && conn.TotalCount > 0
	conn.PageInfo.HasPreviousPage = last != nil && conn.TotalCount > 0
}

I don't think this PR handles all edge cases for the pagination. If you create a query that looks like this:

variants(first: $firstVariant, after: $afterVariant) {
 pageInfo {
 hasNextPage
 endCursor
 }
 }

then we will not populate the pageInfo object correctly. If we request pagination info without any edges, we still need to do the count.

I solved the same problem using an external template, where I used this logic instead:

ignoredEdges := !hasCollectedField(ctx, edgesField)
needTotalCount := hasCollectedField(ctx, totalCountField)
needPageInfo := hasCollectedField(ctx, pageInfoField)
hasPagination := after != nil || first != nil || before != nil || last != nil
if (needTotalCount && hasPagination) || (ignoredEdges && (needTotalCount || needPageInfo)) {
	c := {{ $r }}.Clone()
	{{- /* Clear the selection fields before counting to avoid generating invalid queries. */}}
	c.ctx.Fields = nil
	if conn.TotalCount, err = c.Count(ctx); err != nil {
		return nil, err
	}
	conn.PageInfo.HasNextPage = first != nil && conn.TotalCount > 0
	conn.PageInfo.HasPreviousPage = last != nil && conn.TotalCount > 0
}

Thanks for your post, I’ll give it a try.