feat(database): Add user_id and dttm composite index to Log model.

[xneg]

SUMMARY

When opening welcome page (/superset/welcome/) it took between 10 and 20 seconds to show first results. This is because of /superset/recent_activity endpoint and query against logs table inside it. To speed up this query I suggest to add composite index from user_id and dttm to this table.

ADDITIONAL INFORMATION

• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested

[codecov]

Codecov Report

Merging #19532 (4e305bf) into master (1eef923) will decrease coverage by 12.71%.
The diff coverage is n/a.

❗ Current head 4e305bf differs from pull request most recent head 1201780. Consider uploading reports for the commit 1201780 to get more accurate results

@@             Coverage Diff             @@
##           master   #19532       +/-   ##
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- Coverage   66.60%   53.88%   -12.72%     
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  Files        1678     1678               
  Lines       64246    64246               
  Branches     6539     6539               
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- Hits        42788    34616     -8172     
- Misses      19763    27935     +8172     
  Partials     1695     1695               

Flag	Coverage Δ
hive	52.70% <ø> (ø)
mysql	?
postgres	?
presto	52.55% <ø> (ø)
python	56.50% <ø> (-25.90%)	⬇️
sqlite	?
unit	47.20% <ø> (ø)

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Impacted Files	Coverage Δ
superset/utils/dashboard_import_export.py	0.00% <0.00%> (-100.00%)	⬇️
superset/key_value/commands/upsert.py	0.00% <0.00%> (-89.59%)	⬇️
superset/key_value/commands/update.py	0.00% <0.00%> (-89.37%)	⬇️
superset/key_value/commands/delete.py	0.00% <0.00%> (-85.30%)	⬇️
superset/key_value/commands/delete_expired.py	0.00% <0.00%> (-80.77%)	⬇️
superset/dashboards/commands/importers/v0.py	14.79% <0.00%> (-75.15%)	⬇️
superset/datasets/commands/importers/v0.py	24.82% <0.00%> (-68.80%)	⬇️
superset/databases/commands/test_connection.py	31.42% <0.00%> (-68.58%)	⬇️
superset/datasets/commands/update.py	25.88% <0.00%> (-68.24%)	⬇️
superset/datasets/commands/create.py	30.18% <0.00%> (-67.93%)	⬇️
... and 263 more

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[ktmud]

LGTM. Although I do wonder what's the implication of having this index on the write performance for logs.

In the long run, we should probably design two separate tables for different types of logs---one for online display such as auditing logs and recent activities, another for offline analysis such as page loading performance.