small performance improvement on product listing

[apasare]

Description (*)

Get rid of unnecessary reviews queries on product listing:
"select review_entity_summary.* from review_entity_summary where (review_entity_summary.entity_pk_value = ?) and (store_id = ?)"
This query was executed for each product on listing which didn't have a review summary(@see: Magento\Review\Model\Review::appendSummary and Magento\Review\Block\Product\ReviewRenderer::getReviewsSummaryHtml)

Manual testing scenarios (*)

1. Use a profiler(e.g. blackfire)
2. Go to any product listing page(category page)
3. After profiling the product listing page you should notice that for each product which doesn't have a review an additional sql query is executed: "select review_entity_summary.* from review_entity_summary where (review_entity_summary.entity_pk_value = ?) and (store_id = ?)"

E.g.: if on your product listing page you are listing 20 products, and 3 products have reviews, you will see 17 x "select review_entity_summary.* from review_entity_summary where (review_entity_summary.entity_pk_value = ?) and (store_id = ?)"

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @godvsdeity. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

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[magento-engcom-team]

Hi @miguelbalparda, thank you for the review.
ENGCOM-3437 has been created to process this Pull Request

[magento-engcom-team]

@godvsdeity thank you for contributing. Please accept Community Contributors team invitation here to gain extended permissions for this repository.

[magento-engcom-team]

Hi @godvsdeity. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.