Add index to DateTimeIndexEntity table index_from column

[ellykits]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #1944

Description
Index the column that contains _lastUpdatedAt date to improve performance on search/sorting

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[aditya-07]

@ellykits Can you please confirm that the index works as expected while sorting data.

[aditya-07]

During the testing on my end, I found that the query plan seems to skip this index (_lastUpdatedAt) when used to sort data. But it looks like even though the query plan seems to skip it, having this index makes the query faster See _lastUpdatedAt Performance Tests discussion.

[ellykits]

I'm okay with merging this @jingtang10

[aditya-07]

@ellykits Can you please update the branch to latest.

[ellykits]

During the testing on my end, I found that the query plan seems to skip this index (_lastUpdatedAt) when used to sort data. But it looks like even though the query plan seems to skip it, having this index makes the query faster See _lastUpdatedAt Performance Tests discussion.

Got the following response from this query that searches & sort Groups resources to confirm @aditya-07's observation.

EXPLAIN QUERY PLAN SELECT a.serializedResource
FROM ResourceEntity a
         LEFT JOIN DateIndexEntity b
                   ON a.resourceType = b.resourceType AND a.resourceUuid = b.resourceUuid AND b.index_name = '_lastUpdated'
         LEFT JOIN DateTimeIndexEntity c
                   ON a.resourceType = c.resourceType AND a.resourceUuid = c.resourceUuid AND c.index_name = '_lastUpdated'
WHERE a.resourceType = 'Group'
  AND a.resourceUuid IN (SELECT resourceUuid
                         FROM TokenIndexEntity
                         WHERE resourceType = 'Group'
                           AND index_name = 'type'
                           AND (index_value = 'person' AND IFNULL(index_system, '') = 'http://hl7.org/fhir/group-type'))
  AND a.resourceUuid IN (SELECT resourceUuid
                         FROM TokenIndexEntity
                         WHERE resourceType = 'Group'
                           AND index_name = 'code'
                           AND (index_value = '35359004' AND IFNULL(index_system, '') = 'https://www.snomed.org'))
ORDER BY b.index_from DESC, c.index_from DESC
LIMIT 10 OFFSET 0;

12	0	0	SEARCH a USING INDEX index_ResourceEntity_resourceType_resourceId (resourceType=?)
20	0	0	LIST SUBQUERY 1
23	20	0	SEARCH TokenIndexEntity USING INDEX index_TokenIndexEntity_resourceType_index_name_index_system_index_value (resourceType=? AND index_name=?)
46	0	0	LIST SUBQUERY 2
49	46	0	SEARCH TokenIndexEntity USING INDEX index_TokenIndexEntity_resourceType_index_name_index_system_index_value (resourceType=? AND index_name=?)
69	0	0	SEARCH b USING INDEX index_DateIndexEntity_resourceType_index_name_index_from_index_to (resourceType=? AND index_name=?) LEFT-JOIN
80	0	0	SEARCH c USING INDEX index_DateTimeIndexEntity_resourceType_index_name_index_from_index_to (resourceType=? AND index_name=?) LEFT-JOIN
112	0	0	USE TEMP B-TREE FOR ORDER BY

[aditya-07]

Approving it based on @ellykits and @ekigamba 's findings.

[jingtang10]

Hi @ellykits - can you fix this test: migrate1To2_should_not_throw_exception? This is what's stopping the code from being merged.

[aditya-07]

Left a small comment, otherwise looks good.

[aditya-07]

LGTM