SQL Interface to Query
[Query: Querying for Objects]

Detailed Description

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; INSERT INTO SomeObj (param_a, param_b, param_c) VALUES ("value_a", true, "0/1");

For SELECT, the returned list is a list of all of the instances of 'SomeObj' that match 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.

For INSERT, the returned list is a list containing the newly created instance of 'SomeObj'.

Joins are not supported directly. SELECT * FROM ObjA,ObjB WHERE (ObjA.param_id = ObjB.param_other_id); 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.

However, by repeating queries and adding the entities to a new session using qof_entity_copy_list, a series of queries can be added to a single book. e.g. You can insert multiple entities and save out as a QSF XML file or use multiple SELECT queries to build a precise list - this can be used to replicate most of the functionality of a SQL join.

SELECT * from ObjA where param_id = value; SELECT * from ObjB where param_other_id = value;

Equivalent to: SELECT * from ObjA,ObjB where param_id = param_other_id and param_id = value;

When combined with a foreach callback on the value of param_id for each entity in the QofBook, you can produce the effect of a join from running the two SELECT queries for each value of param_id held in 'value'.

See QofEntityForeachCB and qof_object_foreach.

Date queries handle full date and time strings, using the format exported by the QSF backend. To query dates and times, convert user input into UTC time using the QOF_UTC_DATE_FORMAT string. See qof_date_print

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. (Linas)

XXX (Neil W). Alternatively, I need to use something like this when converting QOF objects between applications by using the returned parameter values to create a second object. One application using QOF could register objects from two applications and convert data from one to the other by using SELECT a,b,c FROM ObjA; SELECT d,f,k FROM ObjB; qof_object_new_instance(); ObjC_set_a(value_c); ObjC_set_b(value_k) etc. What's needed is for the SELECT to return a complete object that only contains the parameters selected.

Also unsupported: UPDATE.

Certain SQL commands can have no QOF equivalent and will generate a runtime parser error:


typedef struct _QofSqlQuery QofSqlQuery


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 gchar *str)
 Perform the query, return the results.
void qof_sql_query_parse (QofSqlQuery *query, const gchar *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.

Definition at line 92 of file qofsql.c.

00093 {
00094     if (!q)
00095         return NULL;
00096     return q->qof_query;
00097 }

QofSqlQuery* qof_sql_query_new ( void   ) 

Create a new SQL-syntax query machine.

Definition at line 64 of file qofsql.c.

00065 {
00066     QofSqlQuery *sqn = (QofSqlQuery *) g_new0 (QofSqlQuery, 1);
00068     sqn->qof_query = NULL;
00069     sqn->parse_result = NULL;
00070     sqn->book = NULL;
00071     sqn->single_global_tablename = NULL;
00072     sqn->kvp_join = NULL;
00074     return sqn;
00075 }

void qof_sql_query_parse ( QofSqlQuery *  query,
const gchar *  str 

Same qof_sql_query_run, 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.

Definition at line 1078 of file qofsql.c.

01079 {
01080     GList *results;
01082     if (!query)
01083         return NULL;
01085     if (NULL == query->qof_query)
01086         return NULL;
01088     qof_query_set_book (query->qof_query, query->book);
01090     /* Maybe log this sucker */
01091     if (qof_log_check (log_module, QOF_LOG_DETAIL))
01092     {
01093         qof_query_print (query->qof_query);
01094     }
01096     results = qof_query_run (query->qof_query);
01098     return results;
01099 }

GList* qof_sql_query_run ( QofSqlQuery *  query,
const gchar *  str 

Perform the query, return the results.

The book must be set in order to be able to perform a query.

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

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).

Definition at line 102 of file qofsql.c.

00103 {
00104     if (!q)
00105         return;
00106     q->book = book;
00107 }

void qof_sql_query_set_kvp ( QofSqlQuery *  ,

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.

Definition at line 112 of file qofsql.c.

00113 {
00114     if (!q)
00115         return;
00116     q->kvp_join = kvp;
00117 }

Generated on Thu Jan 31 22:50:27 2008 for QOF by  doxygen 1.5.4