magento2 search_tmp join leads to empty results in category listing

To debug this, temporarily change createTemporaryTable to createTable in

\Magento\Framework\Search\Adapter\Mysql\TemporaryStorage::createTemporaryTable

    $table->setOption('type', 'memory');
    $connection->createTable($table); // changed
    return $table;
}

No you will be able to inspect the table with other MySQL tools such as PhpMyAdmin.

In my case the table was empty, so I further debugged:

\Magento\Framework\Search\Adapter\Mysql\Adapter::query

and had a look at the $query variable (via Evaluate in the Debugger (string)$query)

The lead to the following query:

 SELECT `main_select`.`entity_id`, MAX(score) AS `relevance` FROM (SELECT `search_index`.`entity_id`, (((0) + (0)) * 1) AS `score` FROM `catalogsearch_fulltext_scope4` AS `search_index`
 LEFT JOIN `catalog_eav_attribute` AS `cea` ON search_index.attribute_id = cea.attribute_id
 INNER JOIN `catalog_category_product_index` AS `category_ids_index` ON search_index.entity_id = category_ids_index.product_id
 LEFT JOIN `catalog_product_index_eav` AS `capacity_filter` ON search_index.entity_id = capacity_filter.entity_id AND capacity_filter.attribute_id = 142 AND capacity_filter.store_id = 1
 LEFT JOIN `cataloginventory_stock_status` AS `capacity_filter_stock` ON capacity_filter_stock.product_id = capacity_filter.source_id
 LEFT JOIN `cataloginventory_stock_status` AS `stock_index` ON search_index.entity_id = stock_index.product_id AND stock_index.website_id = 0 WHERE (stock_index.stock_status = 1) AND (category_ids_index.category_id = 28) AND (capacity_filter.value = '30' AND capacity_filter_stock.stock_status = 1)) AS `main_select` GROUP BY `entity_id` ORDER BY `relevance` DESC
 LIMIT 10000

There is a wrong store ID in there (1) while I am in store 4 - when changing the store ID to 4, it works.

The query is built in

\Magento\Framework\Search\Adapter\Mysql\Mapper::buildQuery

Goes down to

\Magento\CatalogSearch\Model\Search\FilterMapper\TermDropdownStrategy::apply

Here is as bug:

    $joinCondition = sprintf(
        'search_index.entity_id = %1$s.entity_id AND %1$s.attribute_id = %2$d AND %1$s.store_id = %3$d',
        $alias,
        $attribute->getId(),
        $this->storeManager->getWebsite()->getId()
    );

Website ID is taken as store ID

The bug is fixed in Magento master:

https://github.com/magento/magento2/commit/2c62aa376eeed447e632aedb42085c9d255520df

This was caused improperly build index catalogsearch_fulltext, indexer_id in indexer_state table was in working state, this should be changed to invalid and reindexed.

TIP FOR THOSE WHO STRUGGLING WITH SAME PROBLEM:

also, temporary table return zero results if products are out of stock or stock qty are 0