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   slapd-sql    ( 5 )

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TYPICAL SQL BACKEND OPERATION

Having meta-information loaded, the SQL backend uses these tables to determine a set of primary keys of candidates (depending on search scope and filter). It tries to do it for each objectclass registered in ldap_objclasses.

Example: for our query with filter (telephoneNumber=123*) we would get the following query generated (which loads candidate IDs)

SELECT ldap_entries.id,persons.id, 'person' AS objectClass, ldap_entries.dn AS dn FROM ldap_entries,persons,phones WHERE persons.id=ldap_entries.keyval AND ldap_entries.objclass=? AND ldap_entries.parent=? AND phones.pers_id=persons.id AND (phones.phone LIKE '%1%2%3%')

(for ONELEVEL search) or "... AND dn=?" (for BASE search) or "... AND dn LIKE '%?'" (for SUBTREE)

Then, for each candidate, we load the requested attributes using per-attribute queries like

SELECT phones.phone AS telephoneNumber FROM persons,phones WHERE persons.id=? AND phones.pers_id=persons.id

Then, we use test_filter() from the frontend API to test the entry for a full LDAP search filter match (since we cannot effectively make sense of SYNTAX of corresponding LDAP schema attribute, we translate the filter into the most relaxed SQL condition to filter candidates), and send it to the user.

ADD, DELETE, MODIFY and MODRDN operations are also performed on per-attribute meta-information (add_proc etc.). In those fields one can specify an SQL statement or stored procedure call which can add, or delete given values of a given attribute, using the given entry keyval (see examples -- mostly PostgreSQL, ORACLE and MSSQL - since as of this writing there are no stored procs in MySQL).

We just add more columns to ldap_oc_mappings and ldap_attr_mappings, holding statements to execute (like create_proc, add_proc, del_proc etc.), and flags governing the order of parameters passed to those statements. Please see samples to find out what are the parameters passed, and other information on this matter - they are self-explanatory for those familiar with the concepts expressed above.