Function optimizeQuery

packages/db/src/query/optimizer.ts:193–234

(query: QueryIR)

 * ```
 */
export function optimizeQuery(query: QueryIR): OptimizationResult {
  if (query.from.type === `unionAll`) {
    return {
      optimizedQuery: {
        ...query,
        from: new UnionAllClass(
          query.from.queries.map(
            (branch) => optimizeQuery(branch).optimizedQuery,
          ),
        ),
      },
      sourceWhereClauses: new Map(),
    }
  }

  // First, extract source WHERE clauses before optimization
  const sourceWhereClauses = extractSourceWhereClauses(query)

  // Apply multi-level predicate pushdown with iterative convergence
  let optimized = query
  let previousOptimized: QueryIR | undefined
  let iterations = 0
  const maxIterations = 10 // Prevent infinite loops

  // Keep optimizing until no more changes occur or max iterations reached
  while (
    iterations < maxIterations &&
    !deepEquals(optimized, previousOptimized)
  ) {
    previousOptimized = optimized
    optimized = applyRecursiveOptimization(optimized)
    iterations++
  }

  // Remove redundant subqueries
  const cleaned = removeRedundantSubqueries(optimized)

  return {
    optimizedQuery: cleaned,
    sourceWhereClauses,
  }
}

/**
 * Extracts collection-specific WHERE clauses from a query for index optimization.