Support sqlite stdlib functions

[hakobera]

Add SQLite function catalogs listed in below pages.

• https://www.sqlite.org/lang_aggfunc.html
• https://www.sqlite.org/lang_mathfunc.html
• https://www.sqlite.org/lang_corefunc.html

Task

• Move existing builtins end to end test to builtins/postgresql
• Add function catalogs for SQLite
  • Aggregate functions
  • Mathematical functions
  • Scalar functions
• Add end to end test

Remarks

Due to current SQLite parser limitation, we can't get correct type of arguments of function, so we can't overload function based on argument type like below.

SELECT max(1); => integer
SELECT max(1.0); => real
SELECT max('text'); => text

So arguments and return types of these functions like max are defined as any type due to this limitation.

[kyleconroy]

This will change quite a bit of generated code. Is it documented that SQLite will always return an int here?

[hakobera]

In SQLite world, bigint and integer is totally same. SQLite can understand bigint but it's just a alias.
Each column in an SQLite 3 database is assigned one of the following type affinities:

• TEXT
• NUMERIC
• INTEGER
• REAL
• BLOB

And bigint is translate it to integer.

https://www.sqlite.org/datatype3.html

Type definition in sqlc is same. Both are translated to int64 in go world, so this change doesn't any impact for generated code.

https://github.com/kyleconroy/sqlc/blob/0dc2c81f73534c15120f5711f2aa662a5689e02b/internal/codegen/golang/sqlite_type.go#L17-L21

I confirmed generated code is not changed.

https://github.com/hakobera/sqlc/blob/support-sqlite-stdlib-functions/internal/endtoend/testdata/count_star/sqlite/go/query.sql.go#L27-L32

So to keep consistency, I want to use integer for all integer value for SQLite, because it's a true type for integer value. What do you think?