How to re-index all content for the core search engine?

Is there a way to re-index all content for the core search engine?

In older versions, you could reindex with drush:

drush search-reindex --immediate --verbose

However, this does not appear to be an option anymore. In more recent versions of drush, one can do this:

drush search-api-reindex

However, that command is for the Search API module, and not for the core search index.

How do I re-index the core search index in bulk? Cron will only index up to 500 items at a time, but I have tens of thousands of items to index.

You can use the search index service directly

drush ev "\Drupal::service('search.index')->markForReindex();"

and then run drush cron as often as you need to.

In a Bash loop for example:

for (( c=1; c<=5; c++ )); do drush cron; done

Here is some opinioned solution with automation based on @4uk4 answer.

remaining=$(drush ev "echo \Drupal::database()->query('SELECT COUNT(DISTINCT [n].[nid]) FROM {node} [n] LEFT JOIN {search_dataset} [sd] ON [sd].[sid] = [n].[nid] AND [sd].[type] = :type WHERE [sd].[sid] IS NULL OR [sd].[reindex] <> 0', [':type' => 'node'])->fetchField();"); \
size="$(drush cget search.settings index.cron_limit --format=string)"; \
iterations=$(( remaining/$size )); \
for (( c=1; c<=$iterations; c++ )); do printf "work on iteration $c/$iterations\n"; drush cron; done

In this "one line" script we get remaining items for indexing and calculate number of iterations. Then just running cron.

Note: remaining items query from the above is for nodes only.

BTW: you can control "Number of items to index per cron run" by drush config:set command.

Note: This script works well, but you will have to change this piece of code: [':type' => 'node'] to [':type' => 'node_search'] for Drupal 9.x