Please check indexer.log and see if any documents skipped for indexing due to size limitations.
If you have array of array of 10K elements of huge documents it takes time.
You can also try following option.
SELECT ps
FROM activity USE KEYS ["d2f058d3a8d0daa6535bcbf3abfc4819"]
ps = ARRAY {pin.pin_id, pin.images, pin.identifier} FOR pin IN pins WHEN pin.identifier="83017b49ea3a4d8a9501c828de21286a" END
WHERE ARRAY_LENGTH(ps) > 0 ;