Avoid loading DB for commands where it's not necessary.

[nicktobey]

This PR avoids loading dolt DBs at startup, instead waiting for either DoltEnv.ReloadDB or MultiRepoEnv.ReloadDBs to be called.

Based on the specific subcommand being run:

• MultiRepoEnv.ReloadDBs is called prior to command execution if the command will always need DB access.
• Commands that conditionally require a DB can choose whether to call DoltEnv.ReloadDB
• Commands that never need the DB will never load it.

Commands that make use of CliContext don't need to load the DB, as the underlying query engine will load the DB if it needs database access. As a result, commands that are implemented purely in terms of the CliContext will load the DB when Dolt is runnning an embedded SQL engine, and will skip loading the DB when Dolt is connecting to a running server.

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
5355928	ok	5937457

version	total_tests
5355928	5937457

correctness_percentage
100.0

[macneale4]

still a few questions. Overall, this is definitely an improvement.

Also, looks like all the tests are failing. Maybe because of the infinite recurssion?

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
f78cc0d	ok	5937457

version	total_tests
f78cc0d	5937457

correctness_percentage
100.0

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
8b10e7f	ok	5937457

version	total_tests
8b10e7f	5937457

correctness_percentage
100.0

[macneale4]

Only remaining concern is that we'll have multiple threads initializing the DB at the same time. Convince me that's not the case, or guard against it.

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
d27b998	ok	5937457

version	total_tests
d27b998	5937457

correctness_percentage
100.0

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
b1aa361	ok	5937457

version	total_tests
b1aa361	5937457

correctness_percentage
100.0

[coffeegoddd]

@nicktobey DOLT

comparing_percentages
100.000000 to 100.000000

version	result	total
2911085	ok	5937457

version	total_tests
2911085	5937457

correctness_percentage
100.0

[macneale4]

LGTM! There is a Doltgres integration test failing which you should fix before you ship it.

[github-actions]

@coffeegoddd DOLT

test_name	detail	row_cnt	sorted	mysql_time	sql_mult	cli_mult
batching	LOAD DATA	10000	1	0.06	1.67
batching	batch sql	10000	1	0.08	1.5
batching	by line sql	10000	1	0.08	1.5
blob	1 blob	200000	1	0.89	3.99	4.71
blob	2 blobs	200000	1	0.89	4.43	4.93
blob	no blob	200000	1	0.92	2.4	2.82
col type	datetime	200000	1	0.85	2.39	2.68
col type	varchar	200000	1	0.74	3.16	3.59
config width	2 cols	200000	1	0.83	2.41	2.78
config width	32 cols	200000	1	1.87	2.07	2.77
config width	8 cols	200000	1	1	2.35	2.7
pk type	float	200000	1	0.9	2.27	3.01
pk type	int	200000	1	0.82	2.45	2.72
pk type	varchar	200000	1	3.01	0.86	0.91
row count	1.6mm	1600000	1	5.73	2.92	2.92
row count	400k	400000	1	1.49	2.77	2.88
row count	800k	800000	1	2.94	2.82	2.85
secondary index	four index	200000	1	3.76	1.33	1.23
secondary index	no secondary	200000	1	0.92	2.43	2.82
secondary index	one index	200000	1	1.18	2.35	2.42
secondary index	two index	200000	1	2.06	1.7	1.8
sorting	shuffled 1mm	1000000	0	4.93	2.9	2.77
sorting	sorted 1mm	1000000	1	4.81	2.96	2.84

[github-actions]

@coffeegoddd DOLT

name	detail	mean_mult
dolt_blame_basic	system table	1.22
dolt_blame_commit_filter	system table	2.98
dolt_commit_ancestors_commit_filter	system table	0.66
dolt_commits_commit_filter	system table	1.05
dolt_diff_log_join_from_commit	system table	2.77
dolt_diff_log_join_to_commit	system table	2.74
dolt_diff_table_from_commit_filter	system table	1.2
dolt_diff_table_to_commit_filter	system table	1.18
dolt_diffs_commit_filter	system table	1.06
dolt_history_commit_filter	system table	1.37
dolt_log_commit_filter	system table	1.05

[github-actions]

@coffeegoddd DOLT

name	add_cnt	delete_cnt	update_cnt	latency
adds_only	60000	0	0	1.12
adds_updates_deletes	60000	60000	60000	4.45
deletes_only	0	60000	0	2.41
updates_only	0	0	60000	2.99