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SQL Interface to Query
[Query: Querying for Objects]


Typedefs

typedef _QofSqlQuery QofSqlQuery

Functions

QofSqlQuery * qof_sql_query_new (void)
void qof_sql_query_destroy (QofSqlQuery *)
void qof_sql_query_set_book (QofSqlQuery *q, QofBook *book)
GList * qof_sql_query_run (QofSqlQuery *query, const char *str)
void qof_sql_query_parse (QofSqlQuery *query, const char *str)
QofQueryqof_sql_query_get_query (QofSqlQuery *)
GList * qof_sql_query_rerun (QofSqlQuery *query)
void qof_sql_query_set_kvp (QofSqlQuery *, KvpFrame *)


Function Documentation

QofQuery* qof_sql_query_get_query QofSqlQuery *   ) 
 

Return the QofQuery form of the previously parsed query.

QofSqlQuery* qof_sql_query_new void   ) 
 

Create a new SQL-syntax query machine.

void qof_sql_query_parse QofSqlQuery *  query,
const char *  str
 

Same as above, but just parse/pre-process the query; do not actually run it over the dataset. The QofBook does not need to be set before calling this function.

GList* qof_sql_query_rerun QofSqlQuery *  query  ) 
 

Run the previously parsed query. The QofBook must be set before this function can be called. Note, teh QofBook can be changed between each successive call to this routine. This routine can be called after either qof_sql_query_parse() or qof_sql_query_run() because both will set up the parse.

GList* qof_sql_query_run QofSqlQuery *  query,
const char *  str
 

Perform the query, return the results. The book must be set in order to be able to perform a query.

The returned list is a list of ... See below ... The returned list will have been sorted using the indicated sort order, (by default ascending order) and trimed to the max_results length. Do NOT free the resulting list. This list is managed internally by QofSqlQuery.

The types of SQL queries that are allowed at this point are very limited. In general, only the following types of queries are supported: SELECT * FROM SomeObj WHERE (param_a < 10.0) AND (param_b = "asdf") SORT BY param_c DESC; The returned list is a list of all of the instances of 'SomeObj' that mathc the query. The 'SORT' term is optional. The 'WHERE' term is optional; but if you don't include 'WHERE', you will get a list of all of the object instances. The Boolean operations 'AND' and 'OR' together with parenthesis can be used to construct arbitrarily nested predicates.

If the param is a KVP frame, then we use a special markup to indicate frame values. The markup should look like /some/kvp/path:value. Thus, for example, SELECT * FROM SomeObj WHERE (param_a < '/some/kvp:10.0') will search for the object where param_a is a KVP frame, and this KVP frame contains a path '/some/kvp' and the value stored at that path is floating-point and that float value is less than 10.0.

The following are types of queries are NOT supported: SELECT a,b,c FROM ... I am thinking of implementing the above as a list of KVP's whose keys would be a,b,c and values would be the results of the search.

Also unsupported are joins: SELECT * FROM ObjA,ObjB WHERE (ObjA.thingy = ObjB.Stuff); The problem with the above is that the search requires a nested search loop, aka a 'join', which is not currently supported in the underlying QofQuery code.

Also unsupported: UPDATE and INSERT.

void qof_sql_query_set_book QofSqlQuery *  q,
QofBook book
 

Set the book to be searched (you can search multiple books) If no books are set, no results will be returned (since there is nothing to search over).

void qof_sql_query_set_kvp QofSqlQuery *  ,
KvpFrame
 

Set the kvp frame to be used for formulating 'indirect' predicates.

Although joins are not supported (see above), there is one special hack that one can use to pass data indirectly into the predicates. This is by using a KVP key name to reference the value to be used for a predicate. Thus, for example, SELECT * FROM SomeObj WHERE (param_a = KVP:/some/key/path); will look up the value stored at '/some/key/path', and use that value to form the actual predicate. So, for example, if the value stored at '/some/key/path' was 2, then the actual query run will be SELECT * FROM SomeObj WHERE (param_a = 2); The lookup occurs at the time that the query is formulated.

The query does *not* take over ownership of the kvp frame, nor does it copy it. Thus, the kvp frame must exist when the query is formulated, and it is the responsibility of the caller to free it when no longer needed.

Note that because this feature is a kind of a hack put in place due to the lack of support for joins, it will probably go away (be deprecated) if/when joins are implemented.


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