Function combineWherePredicates

packages/db/src/query/predicate-utils.ts:206–279

* Helper to combine where predicates with common logic for AND/OR operations

(
  predicates: Array<BasicExpression<boolean>>,
  operation: `and` | `or`,
  simplifyFn: (
    preds: Array<BasicExpression<boolean>>,
  ) => BasicExpression<boolean> | null,
)

 * Helper to combine where predicates with common logic for AND/OR operations
 */
function combineWherePredicates(
  predicates: Array<BasicExpression<boolean>>,
  operation: `and` | `or`,
  simplifyFn: (
    preds: Array<BasicExpression<boolean>>,
  ) => BasicExpression<boolean> | null,
): BasicExpression<boolean> {
  const emptyValue = operation === `and` ? true : false
  const identityValue = operation === `and` ? true : false

  if (predicates.length === 0) {
    return { type: `val`, value: emptyValue } as BasicExpression<boolean>
  }

  if (predicates.length === 1) {
    return predicates[0]!
  }

  // Flatten nested expressions of the same operation
  const flatPredicates: Array<BasicExpression<boolean>> = []
  for (const pred of predicates) {
    if (pred.type === `func` && pred.name === operation) {
      flatPredicates.push(...pred.args)
    } else {
      flatPredicates.push(pred)
    }
  }

  // Group predicates by field for simplification
  const grouped = groupPredicatesByField(flatPredicates)

  // Simplify each group
  const simplified: Array<BasicExpression<boolean>> = []
  for (const [field, preds] of grouped.entries()) {
    if (field === null) {
      // Complex predicates that we can't group by field
      simplified.push(...preds)
    } else {
      // Try to simplify same-field predicates
      const result = simplifyFn(preds)

      // For intersection: check for empty set (contradiction)
      if (
        operation === `and` &&
        result &&
        result.type === `val` &&
        result.value === false
      ) {
        // Intersection is empty (conflicting constraints) - entire AND is false
        return { type: `val`, value: false } as BasicExpression<boolean>
      }

      // For union: result may be null if simplification failed
      if (result) {
        simplified.push(result)
      }
    }
  }