Function groupWhereClauses

packages/db/src/query/optimizer.ts:666–702

* Step 3: Group WHERE clauses by the sources they touch. * * Single-source clauses can be pushed down to subqueries for optimization. * Multi-source clauses must remain in the main query to preserve join semantics. * * @param analyzedClauses - Array of analyzed WHERE clauses * @returns Grouped

(
  analyzedClauses: Array<AnalyzedWhereClause>,
)

 * @returns Grouped clauses ready for optimization
 */
function groupWhereClauses(
  analyzedClauses: Array<AnalyzedWhereClause>,
): GroupedWhereClauses {
  const singleSource = new Map<string, Array<BasicExpression<boolean>>>()
  const multiSource: Array<BasicExpression<boolean>> = []

  // Categorize each clause based on how many sources it touches
  for (const clause of analyzedClauses) {
    if (clause.touchedSources.size === 1 && !clause.hasNamespaceOnlyRef) {
      // Single source clause without namespace-only references - can be optimized
      const source = Array.from(clause.touchedSources)[0]!
      if (!singleSource.has(source)) {
        singleSource.set(source, [])
      }
      singleSource.get(source)!.push(clause.expression)
    } else if (clause.touchedSources.size > 1 || clause.hasNamespaceOnlyRef) {
      // Multi-source clause or namespace-only reference - must stay in main query
      multiSource.push(clause.expression)
    }
    // Skip clauses that touch no sources (constants) - they don't need optimization
  }

  // Combine multiple clauses for each source with AND
  const combinedSingleSource = new Map<string, BasicExpression<boolean>>()
  for (const [source, clauses] of singleSource) {
    combinedSingleSource.set(source, combineWithAnd(clauses))
  }

  // Combine multi-source clauses with AND
  const combinedMultiSource =
    multiSource.length > 0 ? combineWithAnd(multiSource) : undefined

  return {
    singleSource: combinedSingleSource,
    multiSource: combinedMultiSource,
  }
}

/**
 * Step 4: Apply optimizations by lifting single-source clauses into subqueries.