mongoc_collection_copy man page

Performs a deep copy of the collection struct and its configuration. Useful if you intend to call mongoc_collection_set_write_concern, mongoc_collection_set_read_prefs, or mongoc_collection_set_read_concern, and want to preserve an unaltered copy of the struct.

This function does not copy the contents of the collection on the MongoDB server; use the cloneCollection command for that purpose.

A newly allocated mongoc_collection_t that should be freed with mongoc_collection_destroy() when no longer in use.

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