v0.3.0

Implemented enhancements:

• Add IF(), IFNULL(), NULLIF() #527
• Add NOW function #566
• Rule to remove unused columns from projections and pushdown #570
• [Tableau] - Support DEFAULT expression #487
• Reference substring with substr and mid #483

Fixed bugs:

• Add Tableau to SUPPORTED_CLIENTS.md #558
• unsupported syntax: <nil> #553
• IsNullable does not retain null when we return nil in expressions #546
• Check correct usage of Null value #542
• Unable to connect to _example/main.go mem server using Java JDBC driver #319
• Replace one regex by pool of regex matchers. #557
• Implement ifnull and nullif functions. #555
• Add explicit error when ON clause is missed for JOIN statement #554

Closed issues:

• go 1.11.2 doesn't fetch auth #551

Merged pull requests:

• analyzer: fix fields of subqueries too on prune_columns #574
• analyzer: correctly search for subquery used columns #573
• analyzer: add rule to prune unnecessary columns #572
• function: implement NOW function #568
• analyzer: wait until NaturalJoins are resolved on reorder rule #567
• *: fix query cancellation #565
• Fix soundex type #560
• docs: add tableau to supported clients #559
• Make conversion error clearer and less detailed. #556
• Add error for subqueries #552
• Feature/mid substr #548