The result set object is a container for records returned from a target.
ZOOM_resultset ZOOM_connection_search(ZOOM_connection,
ZOOM_query q);
ZOOM_resultset ZOOM_connection_search_pqf(ZOOM_connection c,
const char *q);
void ZOOM_resultset_destroy(ZOOM_resultset r);
Function ZOOM_connection_search creates
a result set given a connection and query.
Destroy a result set by calling
ZOOM_resultset_destroy.
Simple clients may using PQF only may use function
ZOOM_connection_search_pqf in which case
creating query objects is not necessary.
void ZOOM_resultset_option_set (ZOOM_resultset r,
const char *key,
const char *val);
const char *ZOOM_resultset_option_get (ZOOM_resultset r,
const char *key);
size_t ZOOM_resultset_size (ZOOM_resultset r);
Functions ZOOM_resultset_options_set and
ZOOM_resultset_get sets and gets an option
for a result set similar to ZOOM_connection_option_get
and ZOOM_connection_option_set.
The number of hits also called result-count is returned by
function ZOOM_resultset_size.
Table 3.2. ZOOM Result set Options
| Option | Description | Default |
|---|---|---|
| start | Offset of first record to be retrieved from target. First record has offset 0 unlike the protocol specifications where first record has position 1. | 0 |
| count | Number of records to be retrieved. | 0 |
| presentChunk | The number of records to be
requested from the server in each chunk (present requst). The
value 0 means to request all the records in a single chunk.
(The old step
option is also supported for the benefit of old applications.)
| 0 |
| elementSetName | Element-Set name of records.
Most targets should honor element set name B
and F for brief and full respectively.
| none |
| preferredRecordSyntax | Preferred Syntax, such as
USMARC, SUTRS, etc.
| none |
| schema | Schema for retrieval, such as
Gils-schema, Geo-schema, etc.
| none |
| setname | Name of Result Set (Result Set ID). If this option isn't set, the ZOOM module will automatically allocate a result set name. | default |
For servers that support Search Info report, the following
options may be read using ZOOM_resultset_get.
This detailed information is read after a successful search has
completed.
This information is a list of of items, where each item is
information about a term or subquery. All items in the list
are prefixed by
SearchResult.no
where no presents the item number (0=first, 1=second).
Read searchresult.size to determine the
number of items.
Table 3.3. Search Info Report options
| Option | Description |
|---|---|
| searchresult.size | number of search result entries. This option is-nonexistant if no entries are returned by the server. |
searchresult.no.id | sub query ID |
searchresult.no.count | result count for item (number of hits) |
searchresult.no.subquery.term | subquery term |
searchresult.no.interpretation.term
| interpretation term |
searchresult.no.recommendation.term
| recommendation term |
The creation of a result set involves at least a SearchRequest - SearchResponse protocol handshake. Following that, if a sort criteria was specified as part of the query, a SortRequest - SortResponse handshake takes place. Note that it is necessary to perform sorting before any retrieval takes place, so no records will be returned from the target as part of the SearchResponse because these would be unsorted. Hence, piggyback is disabled when sort criteria are set. Following Search - and a possible sort - Retrieval takes place - as one or more Present Requests/Response pairs being transferred.
The API allows for two different modes for retrieval. A high level
mode which is somewhat more powerful and a low level one.
The low level is enabled when searching on a Connection object
for which the settings
smallSetUpperBound,
mediumSetPresentNumber and
largeSetLowerBound are set. The low level mode
thus allows you to precisely set how records are returned as part
of a search response as offered by the Z39.50 protocol.
Since the client may be retrieving records as part of the
search response, this mode doesn't work well if sorting is used.
The high-level mode allows you to fetch a range of records from
the result set with a given start offset. When you use this mode
the client will automatically use piggyback if that is possible
with the target and perform one or more present requests as needed.
Even if the target returns fewer records as part of a present response
because of a record size limit, etc. the client will repeat sending
present requests. As an example, if option start
is 0 (default) and count is 4, and
piggyback is 1 (default) and no sorting criteria
is specified, then the client will attempt to retrieve the 4
records as part the search response (using piggyback). On the other
hand, if either start is positive or if
a sorting criteria is set, or if piggyback
is 0, then the client will not perform piggyback but send Present
Requests instead.
If either of the options mediumSetElementSetName and
smallSetElementSetName are unset, the value
of option elementSetName is used for piggyback
searches. This means that for the high-level mode you only have
to specify one elementSetName option rather than three.
Current version of YAZ does not take advantage of a result set id returned by the SRU server. Future versions might do, however. Since, the ZOOM driver does not save result set IDs any present (retrieval) is transformed to a SRU SearchRetrieveRequest with same query but, possibly, different offsets.
Option schema specifies SRU schema
for retrieval. However, options elementSetName and
preferredRecordSyntax are ignored.
Options start and count
are supported by SRU.
The remaining options
piggyback,
smallSetUpperBound,
largeSetLowerBound,
mediumSetPresentNumber,
mediumSetElementSetName,
smallSetElementSetName are
unsupported.
SRU supports CQL queries, not PQF.
If PQF is used, however, the PQF query is transferred anyway
using non-standard element pQuery in
SRU SearchRetrieveRequest.
Unfortunately, SRU does not define a database setting. Hence,
databaseName is unsupported and ignored.
However, the path part in host parameter for functions
ZOOM_connecton_new and
ZOOM_connection_connect acts as a
database (at least for the YAZ SRU server).