Revert "fix how cast to boolean works to preserve null (#301)" (#304)

This reverts commit 848b4fe.

src/dialect/druidDialect.ts

@@ -83,7 +83,7 @@ export class DruidDialect extends SQLDialect {
     BOOLEAN: {
       NUMBER: '($$ = 1)',
       STRING: `($$ = 'true')`,
-      _: `CASE CAST($$ AS VARCHAR) WHEN '1' THEN TRUE WHEN 'true' THEN TRUE WHEN '0' THEN FALSE WHEN 'false' THEN FALSE END`,
+      _: `(CAST($$ AS VARCHAR) IN ('1','true'))`,
     },
   };
 

test/simulate/simulateDruidSql.mocha.js

@@ -18,7 +18,6 @@
 const { expect } = require('chai');
 
 const plywood = require('../plywood');
-const { sane } = require('../utils');
 
 const { Expression, External, Dataset, TimeRange, $, ply, r, s$ } = plywood;
 
@@ -509,44 +508,6 @@ describe('simulate DruidSql', () => {
     ]);
   });
 
-  it('works with boolean cast', () => {
-    const ex = ply()
-      .apply('diamonds', $('diamonds').filter($('color').in(['red', 'green', 'blue'])))
-      .apply(
-        'Tags',
-        $('diamonds')
-          .split(s$('t.tags').cast('BOOLEAN'), 'B')
-          .apply('count', $('diamonds').count())
-          .sort('$count', 'descending')
-          .limit(10)
-          .select('B', 'count'),
-      );
-
-    const queryPlan = ex.simulateQueryPlan({
-      diamonds: External.fromJS({
-        engine: 'druidsql',
-        version: '0.20.0',
-        source: 'diamonds',
-        timeAttribute: 'time',
-        attributes,
-        allowSelectQueries: true,
-        mode: 'raw',
-      }),
-    });
-
-    expect(queryPlan.length).to.equal(1);
-    expect(queryPlan[0][0].query).to.deep.equal(sane`
-      SELECT
-      CASE CAST((t.tags) AS VARCHAR) WHEN '1' THEN TRUE WHEN 'true' THEN TRUE WHEN '0' THEN FALSE WHEN 'false' THEN FALSE END AS "B",
-      COUNT(*) AS "count"
-      FROM "diamonds" AS t
-      WHERE "color" IN ('red','green','blue')
-      GROUP BY 1
-      ORDER BY "count" DESC
-      LIMIT 10
-    `);
-  });
-
   it('works with mvFilterOnly and mvOverlap', () => {
     const ex = ply()
       .apply('diamonds', $('diamonds'))