Refactor expression to Mongo query translation

The previous approach was simplistic and could result in inefficient queries
in certain edge cases, notably causing MongoDB to not utilize existing indexes
when querying by last inform timestamps given upper and lower bounds. The new
implementation leverages our existing expression minimizer code and can
therefore generate more efficient queries or at least queries that can take
advantage of existing indexes.

test/synth.ts

@@ -0,0 +1,118 @@
+import ava, { TestInterface } from "ava";
+import { minimize, unionDiff } from "../lib/common/expression/synth";
+import { parse, stringify } from "../lib/common/expression/parser";
+import initSqlJs from "sql.js/dist/sql-asm.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));
+  }
+});