bionic (3) mtbl_fileset.3.gz

NAME

       mtbl_fileset - automatic multiple MTBL data file merger

SYNOPSIS

       #include <mtbl.h>

       Fileset objects:

       struct mtbl_fileset *
       mtbl_fileset_init(const char *fname, const struct mtbl_fileset_options *fopt);

       void
       mtbl_fileset_destroy(struct mtbl_fileset **f);

       void
       mtbl_fileset_reload(struct mtbl_fileset *f);

       void
       mtbl_fileset_reload_now(struct mtbl_fileset *f);

       const struct mtbl_source *
       mtbl_fileset_source(struct mtbl_fileset *f);

       Fileset options:

       struct mtbl_fileset_options *
       mtbl_fileset_options_init(void);

       void
       mtbl_fileset_options_destroy(struct mtbl_fileset_options **fopt);

       void
       mtbl_fileset_options_set_merge_func(
               struct mtbl_fileset_options *fopt,
               mtbl_merge_func fp,
               void *clos);

       void
       mtbl_fileset_options_set_reload_interval(
               struct mtbl_fileset_options *fopt,
               uint32_t reload_interval);

DESCRIPTION

       The mtbl_fileset is a convenience interface for automatically maintaining a merged view of a set of MTBL
       data files. The merged entries may be consumed via the mtbl_source(3) and mtbl_iter(3) interfaces.

       mtbl_fileset objects are initialized from a "setfile", which specifies a list of filenames of MTBL data
       files, one per line. Internally, an mtbl_reader object is initialized from each filename and added to an
       mtbl_merger object. The setfile is watched for changes and the addition or removal of filenames from the
       setfile will result in the corresponding addition or removal of mtbl_reader objects.

       Because the MTBL format does not allow duplicate keys, the caller must provide a function which will
       accept a key and two conflicting values for that key and return a replacement value. This function may be
       called multiple times for the same key if the same key is inserted more than twice. See mtbl_merger(3)
       for further details about the merge function.

       mtbl_fileset objects are created with the mtbl_fileset_init() function, which requires the path to a
       "setfile", fname, and a non-NULL fopt argument which has been configured with a merge function fp.
       mtbl_fileset_source() should then be called in order to consume output via the mtbl_source(3) interface.

       Accesses via the mtbl_source(3) interface will implicitly check for updates to the setfile. However, it
       may be necessary to explicitly call the mtbl_fileset_reload() function in order to check for updates,
       especially if files are being removed from the setfile and the mtbl_source is infrequently accessed.

       The mtbl_fileset_reload() function avoids checking for updates more frequently than every reload_interval
       seconds. The mtbl_fileset_reload_now() function can be called to bypass the reload_interval check.

   Fileset options
       merge_func
           See mtbl_merger(3). An mtbl_merger object is used internally for the external sort.

       reload_interval
           Specifies the interval between checks for updates to the setfile, in seconds. Defaults to 60 seconds.

                                                   07/11/2015                                    MTBL_FILESET(3)