single sequence for all metrics sub tables

[kbrock]

Before:
Every metrics_** table had a different sequence.
So inserting directly into a subtable would result in overlapping id values.
We currently insert into the base metrics table, so this is not a problem.

 Column |  Type  |                           Modifiers                            
--------+--------+---------------------------------------------------------------
 id     | bigint | not null default nextval('metric_rollups_01_id_seq'::regclass)

After:
Everymetrics subtable uses the same sequence.
So inserting into any of the metrics tables will get a unique id.

 Column |  Type  |                           Modifiers                            
--------+--------+---------------------------------------------------------------
 id     | bigint | not null default nextval('metric_rollups_id_seq'::regclass)

Rollback does bring back to the previous value

 Column |  Type  |                           Modifiers                            
--------+--------+---------------------------------------------------------------
 id     | bigint | not null default nextval('metric_rollups_01_id_seq'::regclass)

This change allows us to insert directly into the subtable, which is 10x faster than inserting into the common parent table.

/cc @chrisarcand @Fryguy

[chrisarcand]

Seems ok to me.

[Fryguy]

Can you also drop all of the individual sequences? metrics_##_id_seq and metrics_rollups_##_id_seq

Also, since this PR doesn't change the insertion into the main table, I'm assuming that still works as well?

[chessbyte]

@kbrock @Fryguy what is the status of this PR?

[kbrock]

@chessbyte thanks. I had thought this was merged already - will rebase and push again

[Fryguy]

@kbrock Can you address #48 (comment) ?

[kbrock]

ugh. thanks @Fryguy

1. drop and add sequences.
2. yes inserts into the primary table work as it did before
3. fixed cops & code climate duplicate warnings.

[miq-bot]

Checked commit kbrock@130d14c with ruby 2.3.3, rubocop 0.47.1, and haml-lint 0.20.0
1 file checked, 0 offenses detected
Everything looks fine. 🍰

[Fryguy]

@kbrock I just realized that on the down migration I think you also have to update the nextval to the highest id in the table or you'll get duplicates.

[kbrock]

In the old code, we can not create a record in the old tables.
The sequences will overlap.

So we have never created a record there.

Yes we will reset the sequence back to 1. But since they haven't been used up until now, I think they are all 1 anyway.
And if they weren't, then that would be kinda bad - it would mean we have bad data in our metrics tables

[Fryguy]

Ahhhh I see. The only other thing we might want to do is ensure we set the value to the "min value for the region" as opposed to 1. If that happens automatically, then we are good.