Change default data type name from DOUBLE to DOUBLE PRECISION

[katzyn]

EXPLAIN VALUES CAST(2 AS DOUBLE PRECISION);
> VALUES (CAST(2.0 AS DOUBLE))

In the SQL Standard there is no DOUBLE data type and some databases, including Oracle, PostgreSQL, and SQL Server don't accept it. They all accept DOUBLE PRECISION name from the SQL Standard.

H2 usually preserves names of data types when they're used in table definitions as column data types, but H2 always normalizes them into own default names in all expressions (default and generated columns, check constraints, views, etc.). In result, SCRIPT output contains definitions not compatible with other database systems.

The default name of this data type should be standard-compliant.

@grandinj
Do you agree?

[grandinj]

We don't expect SCRIPT output to be used for any other database (at least not without manual tweaking), but that said, I'm not opposed to this

[katzyn]

Yes, the output isn't compatible in many other ways and typically needs some editing. But number of unreasonable deviations can be reduced.