Refactor bool exp synthesizer

It's now more intelligent about generating IS NULL clauses. For example,
instead of 'LOWER(param) IS NULL' it now generates 'param IS NULL'.

test/boolean-expression.ts

@@ -0,0 +1,118 @@
+import ava, { TestInterface } from "ava";
+import { minimize, unionDiff } from "../lib/common/boolean-expression";
+import { parse, stringify } from "../lib/common/expression-parser";
+import initSqlJs from "sql.js";
+
+const test = ava as TestInterface<{
+  query: (filter: string) => Promise<Set<number>>;
+}>;
+
+const STRING_VALUES = [null, "", "a", "ab", "ab10", "ab-10"];
+const DECIMAL_VALUES = [null, 0, -10, 10];
+
+test.before(async (t) => {
+  const sql = await initSqlJs();
+  const db = new sql.Database();
+
+  t.context.query = async (filter: string): Promise<Set<number>> => {
+    const res = db.exec(`SELECT id FROM test WHERE ${filter}`);
+    if (!res.length) return new Set();
+    return new Set(res[0].values.flat());
+  };
+
+  db.run(
+    "CREATE TABLE test (id INTEGER PRIMARY KEY, string STRING, decimal DECIMAL(4,2))"
+  );
+
+  const stmt = db.prepare("INSERT INTO test (string, decimal) VALUES (?, ?)");
+  const count = STRING_VALUES.length * DECIMAL_VALUES.length;
+  for (let i = 0; i < count; ++i) {
+    const str = i % STRING_VALUES.length;
+    const dec = Math.trunc(i / STRING_VALUES.length) % DECIMAL_VALUES.length;
+    stmt.run([STRING_VALUES[str], DECIMAL_VALUES[dec]]);
+  }
+  stmt.free();
+});
+
+function setsEqual(set1: Set<number>, set2: Set<number>): boolean {
+  if (set1.size !== set2.size) return false;
+  for (const s of set1) if (!set2.has(s)) return false;
+  return true;
+}
+
+function getPermutations(...arrs: any[][]): any[][] {
+  const count = arrs.reduce((total, arr) => total * arr.length, 1);
+  const res = [];
+  for (let i = 0; i < count; ++i) {
+    let j = i;
+    const row = [];
+    for (const arr of arrs) {
+      const v = arr[j % arr.length];
+      j = Math.trunc(j / arr.length);
+      row.push(v);
+    }
+    res.push(row);
+  }
+  return res;
+}
+
+test("minimize", async (t) => {
+  const cases: string[] = [];
+
+  cases.push("null");
+  cases.push("false");
+  cases.push("true");
+  cases.push("string");
+  cases.push("(string + decimal) IS NULL");
+  cases.push("(string + decimal) = NULL");
+  cases.push("COALESCE(string, decimal) = 0");
+
+  for (const [s1, s2, s3, op1, op2] of getPermutations(
+    STRING_VALUES.filter((s) => s),
+    STRING_VALUES.filter((s) => s),
+    STRING_VALUES.filter((s) => s),
+    [">", "=", "<"],
+    ["<>", ">="]
+  )) {
+    cases.push(
+      `string ${op1} "${s1}" OR string ='${s2}' OR NOT string ${op2} '${s3}'`
+    );
+  }
+
+  for (const [s1, s2] of getPermutations(
+    STRING_VALUES.filter((s) => s),
+    STRING_VALUES.filter((s) => s)
+  ))
+    cases.push(`string > "${s1}" AND string < '${s2}'`);
+
+  for (const c of cases) {
+    const res1 = await t.context.query(c);
+    const min = stringify(minimize(parse(c), true));
+    const res2 = await t.context.query(min);
+    t.true(setsEqual(res1, res2));
+  }
+});
+
+test("unionDiff", async (t) => {
+  const cases = [
+    "true",
+    "decimal > 0",
+    "decimal > 10",
+    "UPPER(string || decimal) LIKE 'AB10'",
+    "COALESCE(string, decimal) = 0",
+  ];
+
+  for (const [c1, c2] of getPermutations(cases, cases)) {
+    const res1 = await t.context.query(c1);
+    const res2 = await t.context.query(c2);
+    const [union, diff] = unionDiff(parse(c1), parse(c2));
+    const res3 = await t.context.query(stringify(union));
+    const res4 = await t.context.query(stringify(diff));
+
+    const unionSet = new Set([...res1, ...res2]);
+    const diffSet = new Set(Array.from(res2).filter((r) => !res1.has(r)));
+
+    t.true(setsEqual(res3, unionSet));
+    t.true(setsEqual(res4, diffSet));
+  }
+});