ClickHouse data types

[7phs]

ClickHouse has a number of data types that specific for ClickHouse.

This PR includes support of the following data types of ClickHouse:

• Nullable - ClickHouse uses a special data type to allow to store special marker (NULL) that denotes “missing value” alongside normal values. A default value of option related to nullability of values defines that values are not-nullable. Additionally, ClickHouse transforms SQL definition String NULL -> Nullable(String) in DDL of table;
• All integer and unsigned integers and float data types;
• String related data types;
• Date/time data types;
• Non-experimental nested data types: Nested, Tuple (not-named and named), Array, Map;
• LowCardinality - internal representation of other data types to be dictionary-encoded.

[coveralls]

Pull Request Test Coverage Report for Build 9369161985

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 211 of 240 (87.92%) changed or added relevant lines in 3 files are covered.
• 1058 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-0.7%) to 88.802%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/mod.rs	77	86	89.53%
src/ast/data_type.rs	27	47	57.45%

Files with Coverage Reduction	New Missed Lines	%
src/ast/data_type.rs	2	77.46%
tests/sqlparser_snowflake.rs	12	98.09%
tests/sqlparser_postgres.rs	301	87.83%
src/parser/mod.rs	347	93.06%
src/ast/mod.rs	396	80.85%

Totals
Change from base Build 9316234549:	-0.7%
Covered Lines:	25733
Relevant Lines:	28978

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💛 - Coveralls

[alamb]

Thank you for the review @iffyio 🙏

[iffyio]

Left a couple minor comments otherwise LGTM! Thanks @7phs!
cc @alamb

[7phs]

Thanks @iffyio for review!

[alamb]

Thank you @7phs and @iffyio