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

[tutranngoc]

PR Description: Avoid unnecessary COUNT(*) query when resolving pageInfo

When querying a connection with pageInfo, we always execute an extra SQL query (SELECT COUNT(*)). This is not required for computing pageInfo and adds avoidable dat

The build() call in:

conn.build(nodes, pager, after, first, before, last)

already computes cursor fields (startCursor, endCursor) and correctly determines pagination flags (hasNextPage, hasPreviousPage) based on the paging arguments and returned nodes.

Currently we also derive flags using TotalCount, which forces a COUNT(*):

conn.PageInfo.HasNextPage = first != nil && conn.TotalCount > 0
conn.PageInfo.HasPreviousPage = last != nil && conn.TotalCount > 0

This makes every request that includes pageInfo pay for a COUNT(*), even when callers don’t request totalCount and we don’t actually need it.

What this PR changes:

• Stops triggering SELECT COUNT(*) when it’s not needed for pageInfo.
• Relies on the existing build() logic for pageInfo instead of TotalCount.

Why it matters

• Reduces database load by removing redundant COUNT(*) queries.
• Helps prevent query amplification in nested resolvers (a common source of N+1-like behavior).
• Improves latency for list queries that request pageInfo but not totalCount.

Example query affected:

variants(first: $firstVariant, after: $afterVariant) {
    edges {
      cursor
      node {
        id
        title
        barcode
        baseID
        costPrice
        height
      }
    }
    pageInfo {
      hasNextPage
      endCursor
    }
  }

[tutranngoc]

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

[giautm]

@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]

@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.