and distribution of data on different RDBMSes, OSes, hosts etc., in
other words, in highly heterogeneous environment.
.LP
-This backend is experimental.
+This backend is \fIexperimental\fP.
.SH CONFIGURATION
These
.B slapd.conf
-options apply to the SQL backend database.
-That is, they must follow a "database sql" line and come before any
+options apply to the SQL backend database, which means that
+they must follow a "database sql" line and come before any
subsequent "backend" or "database" lines.
-Other database options are described in the
+Other database options not specific to this backend are described
+in the
.BR slapd.conf (5)
manual page.
+.SH DATA SOURCE CONFIGURATION
+
.TP
.B dbname <datasource name>
The name of the ODBC datasource to use.
.LP
.B dbhost <hostname>
.br
-.B dbuser <username>
-.br
.B dbpasswd <password>
+.br
+.B dbuser <username>
.RS
-These three options are generally unneeded, because this information is already
-taken from the datasource.
-Use them if you need to override datasource settings.
+The three above options are generally unneeded, because this information
+is taken from the datasource specified by the
+.B dbname
+directive.
+They allow to override datasource settings.
Also, several RDBMS' drivers tend to require explicit passing of user/password,
even if those are given in datasource (Note:
.B dbhost
is currently ignored).
.RE
+.SH SCOPING CONFIGURATION
+These options specify SQL query templates for scoping searches.
+
.TP
.B subtree_cond <SQL expression>
Specifies a where-clause template used to form a subtree search condition
-(dn=".*<dn>").
+(dn="(.+,)?<dn>$").
It may differ from one SQL dialect to another (see samples).
+By default, it is constructed based on the knowledge about
+how to normalize DN values (e.g.
+\fB"<upper_func>(ldap_entries.dn) LIKE CONCAT('%',?)"\fP);
+see \fBupper_func\fP, \fBupper_needs_cast\fP, \fBconcat_pattern\fP
+and \fBstrcast_func\fP in "HELPER CONFIGURATION" for details.
+
.TP
.B children_cond <SQL expression>
Specifies a where-clause template used to form a children search condition
-(dn="\.+,<dn>").
+(dn=".+,<dn>$").
It may differ from one SQL dialect to another (see samples).
+By default, it is constructed based on the knowledge about
+how to normalize DN values (e.g.
+\fB"<upper_func>(ldap_entries.dn) LIKE CONCAT('%,',?)"\fP);
+see \fBupper_func\fP, \fBupper_needs_cast\fP, \fBconcat_pattern\fP
+and \fBstrcast_func\fP in "HELPER CONFIGURATION" for details.
+
+.TP
+.B use_subtree_shortcut { NO | yes }
+Do not use the subtree condition when the searchBase is the database
+suffix, and the scope is subtree; rather collect all entries.
+
+.RE
+.SH STATEMENT CONFIGURATION
+These options specify SQL query templates for loading schema mapping
+metainformation, adding and deleting entries to ldap_entries, etc.
+All these and subtree_cond should have the given default values.
+For the current value it is recommended to look at the sources,
+or in the log output when slapd starts with "-d 5" or greater.
+Note that the parameter number and order must not be changed.
+
.TP
.B oc_query <SQL expression>
+The query that is used to collect the objectClass mapping data
+from table \fIldap_oc_mappings\fP; see "METAINFORMATION USED" for details.
The default is
-.B "SELECT id, name, keytbl, keycol, create_proc, delete_proc, expect_return FROM ldap_oc_mappings"
+\fB"SELECT id, name, keytbl, keycol, create_proc, delete_proc, expect_return
+FROM ldap_oc_mappings"\fP.
+
.TP
.B at_query <SQL expression>
+The query that is used to collect the attributeType mapping data
+from table \fIldap_attr_mappings\fP; see "METAINFORMATION USED" for details.
The default is
-.B "SELECT name, sel_expr, from_tbls, join_where, add_proc, delete_proc, param_order, expect_return FROM ldap_attr_mappings WHERE oc_map_id=?"
+\fB"SELECT name, sel_expr, from_tbls, join_where, add_proc, delete_proc,
+param_order, expect_return FROM ldap_attr_mappings WHERE oc_map_id=?"\fP.
+
.TP
-.B insentry_query <SQL expression>
+.B id_query <SQL expression>
+The query that is used to map a DN to an entry
+in table \fIldap_entries\fP; see "METAINFORMATION USED" for details.
The default is
-.B "INSERT INTO ldap_entries (dn, oc_map_id, parent, keyval) VALUES (?, ?, ?, ?)"
+\fB"SELECT id,keyval,oc_map_id,dn FROM ldap_entries WHERE <DN match expr>"\fP,
+where \fB<DN match expr>\fP is constructed based on the knowledge about
+how to normalize DN values (e.g. \fB"dn=?"\fP if no means to uppercase
+strings are available; typically, \fB"<upper_func>(dn)=?"\fP is used);
+see \fBupper_func\fP, \fBupper_needs_cast\fP, \fBconcat_pattern\fP
+and \fBstrcast_func\fP in "HELPER CONFIGURATION" for details.
+
.TP
-.B delentry_query <SQL expression>
+.B insentry_stmt <SQL expression>
+The statement that is used to insert a new entry
+in table \fIldap_entries\fP; see "METAINFORMATION USED" for details.
The default is
-.B "DELETE FROM ldap_entries WHERE id=?"
+\fB"INSERT INTO ldap_entries (dn, oc_map_id, parent, keyval) VALUES
+(?, ?, ?, ?)"\fP.
+
+.TP
+.B delentry_stmt <SQL expression>
+The statement that is used to delete an existing entry
+from table \fIldap_entries\fP; see "METAINFORMATION USED" for details.
+The default is
+\fB"DELETE FROM ldap_entries WHERE id=?"\fP.
+
+.TP
+.B delobjclasses_stmt <SQL expression>
+The statement that is used to delete an existing entry's ID
+from table \fIldap_objclasses\fP; see "METAINFORMATION USED" for details.
+The default is
+\fB"DELETE FROM ldap_entry_objclasses WHERE entry_id=?"\fP.
+
+.RE
+.SH HELPER CONFIGURATION
+These statements are used to modify the default behavior of the backend
+according to issues of the dialect of the RDBMS.
+The first options essentially refer to string and DN normalization
+when building filters.
+LDAP normalization is more than upper- (or lower-)casing everything;
+however, as a reasonable trade-off, for case-sensitive RDBMSes the backend
+can be instructed to uppercase strings and DNs by providing
+the \fBupper_func\fP directive.
+Some RDBMSes, to use functions on arbitrary data types, e.g. string
+constants, requires a cast, which is triggered
+by the \fBupper_needs_cast\fP directive.
+If required, a string cast function can be provided as well,
+by using the \fBstrcast_func\fP directive.
+Finally, a custom string concatenation pattern may be required;
+it is provided by the \fBconcat_pattern\fP directive.
-These four options specify SQL query templates for loading schema mapping
-metainformation, adding and deleting entries to ldap_entries, etc.
-All these and subtree_cond should have the given default values.
-For the current value it is recommended to look at the sources,
-or in the log output when slapd starts with "-d 5" or greater.
-Note that the parameter number and order must not be changed.
.TP
.B upper_func <SQL function name>
Specifies the name of a function that converts a given value to uppercase.
-This is used for CIS matching when the RDBMS is case sensitive.
+This is used for case insensitive matching when the RDBMS is case sensitive.
+It may differ from one SQL dialect to another (e.g. \fBUCASE\fP, \fBUPPER\fP
+or whatever; see samples). By default, none is used, i.e. strings are not
+uppercased, so matches may be case sensitive.
+
.TP
-.B upper_needs_cast { yes | no }
+.B upper_needs_cast { NO | yes }
Set this directive to
.B yes
if
.B upper_func
-needs an explicit cast when applied to literal strings. The form
+needs an explicit cast when applied to literal strings.
+A cast in the form
.B CAST (<arg> AS VARCHAR(<max DN length>))
is used, where
.B <max DN length>
-is builtin.
-This is
-.B experimental
-and may change in future releases.
+is builtin in back-sql; see macro
+.B BACKSQL_MAX_DN_LEN
+(currently 255; note that slapd's builtin limit, in macro
+.BR SLAP_LDAPDN_MAXLEN ,
+is set to 8192).
+This is \fIexperimental\fP and may change in future releases.
+
+.TP
+.B strcast_func <SQL function name>
+Specifies the name of a function that converts a given value to a string
+for appropriate ordering. This is used in "SELECT DISTINCT" statements
+for strongly typed RDBMSes with little implicit casting (like PostgreSQL),
+when a literal string is specified.
+This is \fIexperimental\fP and may change in future releases.
+
.TP
.B concat_pattern <pattern>
This statement defines the
.B pattern
-to be used to concatenate strings. The
+that is used to concatenate strings. The
.B pattern
MUST contain two question marks, '?', that will be replaced
by the two strings that must be concatenated. The default value is
.BR "CAST(?||? AS VARCHAR(<length>))".
On some RDBMSes (IBM db2, MSSQL) the form
.B "?+?"
-is known to work.
+is known to work as well.
Carefully check the documentation of your RDBMS or stay with the examples
for supported ones.
-This is
-.B experimental
-and may change in future releases.
+This is \fIexperimental\fP and may change in future releases.
+
.TP
-.B strcast_func <SQL function name>
-Specifies the name of a function that converts a given value to a string
-for appropriate ordering. This is used in "SELECT DISTINCT" statements
-for strongly typed RDBMSes with little implicit casting (like PostgreSQL),
-when a literal string is specified.
-This is
-.B experimental
-and may change in future releases.
+.B aliasing_keyword <string>
+Define the aliasing keyword. Some RDBMSes use the word "\fIAS\fP"
+(the default), others don't use any.
+
.TP
-.B has_ldapinfo_dn_ru { yes | no }
-Explicitly inform the backend whether the SQL schema has dn_ru column
-(dn in reverse uppercased form) or not.
-Overrides automatic check (required by PostgreSQL/unixODBC).
-This is
-.B experimental
-and may change in future releases.
+.B aliasing_quote <string>
+Define the quoting char of the aliasing keyword. Some RDBMSes
+don't require any (the default), others may require single
+or double quotes.
.TP
-.B fail_if_no_mapping { yes | no }
+.B has_ldapinfo_dn_ru { NO | yes }
+Explicitly inform the backend whether the dn_ru column
+(DN in reverse uppercased form) is present in table \fIldap_entries\fP.
+Overrides automatic check (this is required, for instance,
+by PostgreSQL/unixODBC).
+This is \fIexperimental\fP and may change in future releases.
+
+.TP
+.B fail_if_no_mapping { NO | yes }
When set to
.B yes
-it forces
-.I attribute
-write operations to fail if no appropriate mapping between LDAP attributes
-and SQL data is available.
-The default behavior is to ignore those changes that cannot be mapped
-correctly.
+it forces \fIattribute\fP write operations to fail if no appropriate
+mapping between LDAP attributes and SQL data is available.
+The default behavior is to ignore those changes that cannot be mapped.
It has no impact on objectClass mapping, i.e. if the
.I structuralObjectClass
of an entry cannot be mapped to SQL by looking up its name
operation will fail regardless of the
.B fail_if_no_mapping
switch; see section "METAINFORMATION USED" for details.
-This is
-.B experimental
-and may change in future releases.
+This is \fIexperimental\fP and may change in future releases.
+
+.TP
+.B allow_orphans { NO | yes }
+When set to
+.B yes
+orphaned entries (i.e. without the parent entry in the database)
+can be added. This option should be used with care, possibly
+in conjunction with some special rule on the RDBMS side that
+dynamically creates the missing parent.
+
+.TP
+.B baseObject [ <filename> ]
+Instructs the database to create and manage an in-memory baseObject
+entry instead of looking for one in the RDBMS.
+If the (optional)
+.B <filename>
+argument is given, the entry is read from that file in
+.BR LDIF (5)
+format; otherwise, an entry with objectClass \fBextensibleObject\fP
+is created based on the contents of the RDN of the \fIbaseObject\fP.
+This is particularly useful when \fIldap_entries\fP
+information is stored in a view rather than in a table, and
+.B union
+is not supported for views, so that the view can only specify
+one rule to compute the entry structure for one objectClass.
+This topic is discussed further in section "METAINFORMATION USED".
+This is \fIexperimental\fP and may change in future releases.
+
+.TP
+.B create_needs_select { NO | yes }
+Instructs the database whether or not entry creation
+in table \fIldap_entries\fP needs a subsequent select to collect
+the automatically assigned ID, instead of being returned
+by a stored procedure.
+
+.LP
+.B fetch_attrs <attrlist>
+.br
+.B fetch_all_attrs { NO | yes }
+.RS
+The first statement allows to provide a list of attributes that
+must always be fetched in addition to those requested by any specific
+operation, because they are required for the proper usage of the
+backend. For instance, all attributes used in ACLs should be listed
+here. The second statement is a shortcut to require all attributes
+to be always loaded. Note that the dynamically generated attributes,
+e.g. \fIhasSubordinates\fP, \fIentryDN\fP and other implementation
+dependent attributes are \fBNOT\fP generated at this point, for
+consistency with the rest of slapd. This may change in the future.
+.RE
+
+.TP
+.B check_schema { YES | no }
+Instructs the database to check schema adherence of entries after
+modifications, and structural objectClass chain when entries are built.
+By default it is set to
+.BR yes .
+
+.TP
+.B sqllayer <name> [...]
+Loads the layer \fB<name>\fP onto a stack of helpers that are used
+to map DNs from LDAP to SQL representation and vice-versa.
+Subsequent args are passed to the layer configuration routine.
+This is \fIhighly experimental\fP and should be used with extreme care.
+The API of the layers is not frozen yet, so it is unpublished.
.SH METAINFORMATION USED
.LP
.LP
.nf
SELECT phones.phone AS telephoneNumber FROM persons,phones
- WHERE persons.id=phones.pers_id AND persons.id=?
+ WHERE persons.id=phones.pers_id AND persons.id=?
.fi
.LP
If we wanted to service LDAP requests with filters like
.LP
.nf
SELECT ... FROM persons,phones
- WHERE persons.id=phones.pers_id
- AND persons.id=?
- AND phones.phone like '123%'
+ WHERE persons.id=phones.pers_id
+ AND persons.id=?
+ AND phones.phone like '%1%2%3%'
.fi
.LP
+(note how the telephoneNumber match is expanded in multiple wildcards
+to account for interspersed ininfluential chars like spaces, dashes
+and so; this occurs by design because telephoneNumber is defined after
+a specially recognized syntax).
So, if we had information about what tables contain values for each
attribute, how to join these tables and arrange these values, we could
try to automatically generate such statements, and translate search
.LP
.nf
CREATE VIEW ldap_entries (id, dn, oc_map_id, parent, keyval)
- AS SELECT (1000000000+userid),
- UPPER(CONCAT(CONCAT('cn=',gecos),',o=MyCompany,c=NL')),
- 1, 0, userid FROM unixusers UNION
+ AS
+ SELECT 0, UPPER('o=MyCompany,c=NL'),
+ 3, 0, 'baseObject' FROM unixusers WHERE userid='root'
+ UNION
+ SELECT (1000000000+userid),
+ UPPER(CONCAT(CONCAT('cn=',gecos),',o=MyCompany,c=NL')),
+ 1, 0, userid FROM unixusers
+ UNION
SELECT (2000000000+groupnummer),
- UPPER(CONCAT(CONCAT('cn=',groupnaam),',o=MyCompany,c=NL')),
- 2, 0, groupnummer FROM groups;
+ UPPER(CONCAT(CONCAT('cn=',groupnaam),',o=MyCompany,c=NL')),
+ 2, 0, groupnummer FROM groups;
.fi
+
+.LP
+If your RDBMS does not support
+.B unions
+in views, only one objectClass can be mapped in
+.BR ldap_entries ,
+and the baseObject cannot be created; in this case, see the
+.B baseObject
+directive for a possible workaround.
+
.LP
.SH Typical SQL backend operation
Having metainformation loaded, the SQL backend uses these tables to
AND ldap_entries.objclass=?
AND ldap_entries.parent=?
AND phones.pers_id=persons.id
- AND (phones.phone LIKE '123%')
+ AND (phones.phone LIKE '%1%2%3%')
.fi
.LP
(for ONELEVEL search)
metainformation (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 ORACLE and MSSQL - since
-there're no stored procs in mySQL).
+the given entry keyval (see examples -- mostly PostgreSQL, ORACLE and MSSQL
+- since as of this writing there are no stored procs in MySQL).
.LP
-We just add more columns to oc_mappings and attr_mappings, holding
+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 concept expressed above.
+with the concepts expressed above.
.LP
.SH Common techniques (referrals, multiclassing etc.)
First of all, let's remember that among other major differences to the
complete LDAP data model, the concept above does not directly support
such things as multiple objectclasses per entry, and referrals.
Fortunately, they are easy to adopt in this scheme.
-The SQL backend suggests two more tables being added to the schema -
-ldap_entry_objectclasses(entry_id,oc_name), and
-ldap_referrals(entry_id,url).
+The SQL backend suggests one more table being added to the schema:
+ldap_entry_objectclasses(entry_id,oc_name).
.LP
The first contains any number of objectclass names that corresponding
entries will be found by, in addition to that mentioned in
So, you may, for instance, have a mapping for inetOrgPerson, and use it
for queries for "person" objectclass...
.LP
-The second table contains any number of referrals associated with a given entry.
-The SQL backend automatically adds attribute mapping for "ref" attribute
-to each objectclass mapping that loads values from this table.
-So, if you add objectclass "referral" to this entry, and make one or
-more tuples in ldap_referrals for this entry (they will be seen as
-values of "ref" attribute), you will have slapd return a referral, as
-described in the Administrators Guide.
+Referrals used to be implemented in a loose manner by adding an extra
+table that allowed any entry to host a "ref" attribute, along with
+a "referral" extra objectClass in table ldap_entry_objclasses.
+In the current implementation, referrals are treated like any other
+user-defined schema, since "referral" is a structural objectclass.
+The suggested practice is to define a "referral" entry in ldap_oc_mappings,
+holding a naming attribute, e.g. "ou" or "cn", a "ref" attribute,
+containing the url; in case multiple referrals per entry are needed,
+a separate table for urls can be created, where urls are mapped
+to the respective entries.
+The use of the naming attribute usually requires to add
+an "extensibleObject" value to ldap_entry_objclasses.
+
.LP
.SH Caveats
As previously stated, this backend should not be considered
a replacement of other data storage backends, but rather a gateway
to existing RDBMS storages that need to be published in LDAP form.
.LP
-The hasSubordintes operational attribute is honored by back-sql
+The \fBhasSubordintes\fP operational attribute is honored by back-sql
in search results and in compare operations; it is partially honored
-also in filtering. Owing to design limitations, a (braindead) filter
+also in filtering. Owing to design limitations, a (brain-dead?) filter
of the form
\fB(!(hasSubordinates=TRUE))\fP
-will give no results instead of returning all the leaf entries.
+will give no results instead of returning all the leaf entries, because
+it actually expands into \fB... AND NOT (1=1)\fP.
If you need to find all the leaf entries, please use
\fB(hasSubordinates=FALSE)\fP
instead.
.LP
+A directoryString value of the form "__First___Last_"
+(where underscores should be replaced by spaces) corresponds
+to its prettified counterpart "First_Last"; this is not currently
+honored by back-sql if non-prettified data is written via RDBMS;
+when non-prettified data is written thru back-sql, the prettified
+values are actually used instead.
+.LP
+.SH PROXY CACHE OVERLAY
+The proxy cache overlay
+allows caching of LDAP search requests (queries) in a local database.
+See
+.BR slapo-pcache (5)
+for details.
.SH EXAMPLES
There are example SQL modules in the slapd/back-sql/rdbms_depend/
directory in the OpenLDAP source tree.
+.SH ACCESS CONTROL
+The
+.B sql
+backend honors access control semantics as indicated in
+.BR slapd.access (5)
+(including the
+.B disclose
+access privilege when enabled at compile time).
.SH FILES
+
.TP
ETCDIR/slapd.conf
default slapd configuration file
projects / openldap / blobdiff