IN () Means Nothing — JavaScript Bug Hunt

Briefing

Inspired by the empty-list crash that has paged every team with a query builder: WHERE id IN () is a syntax error in real databases. The empty case must compile to a query that matches nothing — deliberately.

The mock engine (locked) is as strict as Postgres.

Bug report

BUG-IN-EMPTY · Priority: High · Reported by: batch jobs

selectByIds(ids) -> { sql, params }:

• non-empty: "SELECT * FROM items WHERE id IN (?, ?, …)" with params
• empty: "SELECT * FROM items WHERE 1=0" (matches nothing, no params)

Observed: the nightly job passes an empty batch and the whole run dies on a SQL syntax error.

Logs

[job] SyntaxError: unexpected token ')' in: ... WHERE id IN ()

The code as shipped

src/sql/selectByIds.js (editable)

// Builds the batched select.
exports.selectByIds = function (ids) {
  var marks = ids.map(function () { return "?"; }).join(", ");
  return { sql: "SELECT * FROM items WHERE id IN (" + marks + ")", params: ids };
};

Read-only context: src/sql/engine.js.