CBL-6359: C4 APIs for the ArrayIndex (#2170)

Extended C4IndexOptions to include unnestPath for the ArrayIndex.

Note: c4index_getOptions currently won't get back the unnestPath passed to c4createIndex.

C/include/c4IndexTypes.h

@@ -118,6 +118,11 @@ typedef struct C4IndexOptions {
  separated by spaces. */
  const char* C4NULLABLE stopWords;
 
+ /** The property path to the array property to be unnested. If this property is nested in a
+ parent array property, e.g. interests in students[i].interests[j], the unnestPath would
+ be represented by students[].interests */
+ const char* C4NULLABLE unnestPath;
+
 #ifdef COUCHBASE_ENTERPRISE
  /** Options for vector indexes. */
  C4VectorIndexOptions vector;

LiteCore/Database/CollectionImpl.hh

@@ -398,7 +398,9 @@ namespace litecore {
  IndexSpec::Options options;
  switch ( indexType ) {
  case kC4ValueIndex:
+ break;
  case kC4ArrayIndex:
+ if ( indexOptions ) { options.emplace<IndexSpec::ArrayOptions>(indexOptions->unnestPath); }
  break;
  case kC4FullTextIndex:
  if ( indexOptions ) {

LiteCore/Query/IndexSpec.hh

@@ -43,13 +43,20 @@ namespace litecore {
  const char* stopWords{}; ///< NULL for default, or comma-delimited string, or empty
  };
 
+ /// Options for an ArrayIndex
+ struct ArrayOptions {
+ alloc_slice unnestPath;
+
+ ArrayOptions(string_view unnestPath_) : unnestPath(alloc_slice::nullPaddedString(unnestPath_)) {}
+ };
+
  /// Options for a vector index.
  using VectorOptions = vectorsearch::IndexSpec;
 
  static constexpr vectorsearch::SQEncoding DefaultEncoding{8};
 
  /// Index options. If not empty (the first state), must match the index type.
- using Options = std::variant<std::monostate, FTSOptions, VectorOptions>;
+ using Options = std::variant<std::monostate, FTSOptions, VectorOptions, ArrayOptions>;
 
  /// Constructs an index spec.
  /// @param name_ Name of the index (must be unique in its collection.)
@@ -76,6 +83,8 @@ namespace litecore {
 
  const VectorOptions* vectorOptions() const { return std::get_if<VectorOptions>(&options); }
 
+ const ArrayOptions* arrayOptions() const { return std::get_if<ArrayOptions>(&options); }
+
  /** The required WHAT clause: the list of expressions to index */
  FLArray what() const;