Allow adding sequence table to the vschema via ALTER VSCHEMA ADD SEQU…

[kalfonso]

Currently we can add a table to the vschema via "ALTER VSCHEMA", create a hash, lookup vindex, etc but there is no way to add a sequence table. A second PR will address referencing a sequence table from a sharded keyspace

Signed-off-by: Karel Alfonso Sague kalfonso@squareup.com

[tirsen]

I would just call it “IsSequence”. We know it’s Vitess. :-)

[kalfonso]

I think you can have SQL sequences as well. For instance MariaDB allows "CREATE SEQUENCE" (https://mariadb.com/kb/en/library/create-sequence/). Initially wanted to differentiate.

[tirsen]

I see. I think we don't need to support MariaDB sequences. Wdyt @sougou ?

[demmer]

IMO we don't need a special bit for this -- you can just re-use the VindexSpec and make the vindex "type" equal to "sequence.

[tirsen]

FYI @demmer if you have an opinion on syntax

[sougou]

I'll take a look a this later, but here's an old document to use as reference: https://vitess.io/docs/reference/vitess-sequences/

[kalfonso]

Thanks @sougou I'll update PR to reflect the sequence document instead of going via "alter vschema"

[tirsen]

I think we need an ALTER VSCHEMA statement for sequences.

For the future we could also add a CREATE SEQUENCE statements which collapses three things into the same statement:

1. Create sequence table in the single shard (only works in an unsharded keyspace)
2. Insert the initial row
3. Runs the ALTER VSCHEMA statement in this PR

We won't ever be able to use such a statement though because the way we run DDL against our databases is completely different from how we insert data into them which is completely different from how we change the vschema. Because SOX.

So we still need an ALTER VSCHEMA statement for sequences.

[demmer]

Syntactically since we eventually want to support CREATE SEQUENCE and not CREATE SEQUENCE TABLE, I think this should be ALTER VSCHEMA ADD SEQUENCE table_name.

[kalfonso]

Done

[demmer]

I think we need an ALTER VSCHEMA statement for sequences.
I agree

For the future we could also add a CREATE SEQUENCE statements which collapses three things into the same statement:
Yeah this would be nice too