-.TH SLAPD-SQL 5 "30 April 2002" "OpenLDAP LDVERSION"
+.TH SLAPD-SQL 5 "RELEASEDATE" "OpenLDAP LDVERSION"
.\" $OpenLDAP$
.SH NAME
-slapd-sql \- SQL backend to slapd
+slapd\-sql \- SQL backend to slapd
.SH SYNOPSIS
ETCDIR/slapd.conf
-.SH PURPOSE
-The primary purpose of this backend (8) to
+.SH DESCRIPTION
+The primary purpose of this
.BR slapd (8)
-is to PRESENT information stored in some RDBMS as an LDAP subtree
+backend is to PRESENT information stored in some RDBMS as an LDAP subtree
without any programming (some SQL and maybe stored procedures can't be
considered programming, anyway ;).
.LP
That is, for example, when you (some ISP) have account information you
-use in RDBMS, and want to use modern solutions that expect such
+use in an RDBMS, and want to use modern solutions that expect such
information in LDAP (to authenticate users, make email lookups etc.).
Or you want to synchronize or distribute information between different
sites/applications that use RDBMSes and/or LDAP.
Or whatever else...
.LP
-It is NOT designed as general-purpose backend that uses RDBMS instead
-of BerkeleyDB (as the standard LDBM backend does), though it can be
+It is NOT designed as a general-purpose backend that uses RDBMS instead
+of BerkeleyDB (as the standard BDB backend does), though it can be
used as such with several limitations.
You can take a look at
.B http://www.openldap.org/faq/index.cgi?file=378
-(OpenLDAP FAQ-O-Matic/General LDAP FAQ/Directories vs. conventional
+(OpenLDAP FAQ\-O\-Matic/General LDAP FAQ/Directories vs. conventional
databases) to find out more on this point.
.LP
-The idea (detailed below) is to use some metainformation to translate
+The idea (detailed below) is to use some meta-information to translate
LDAP queries to SQL queries, leaving relational schema untouched, so
that old applications can continue using it without any
modifications.
replication, and exchange data as needed.
.LP
The SQL backend is designed to be tunable to virtually any relational
-schema without having to change source (through that metainformation
+schema without having to change source (through that meta-information
mentioned).
Also, it uses ODBC to connect to RDBMSes, and is highly configurable
for SQL dialects RDBMSes may use, so it may be used for integration
and distribution of data on different RDBMSes, OSes, hosts etc., in
other words, in highly heterogeneous environment.
+.LP
+This backend is \fIexperimental\fP.
+.SH CONFIGURATION
+These
+.B slapd.conf
+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 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 dbpasswd <password>
+.br
+.B dbuser <username>
+.RS
+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>$").
+It may differ from one SQL dialect to another (see samples).
+By default, it is constructed based on the knowledge about
+how to normalize DN values (e.g.
+\fB"<upper_func>(ldap_entries.dn) LIKE CONCAT('%',?)"\fP);
+see \fBupper_func\fP, \fBupper_needs_cast\fP, \fBconcat_pattern\fP
+and \fBstrcast_func\fP in "HELPER CONFIGURATION" for details.
+
+.TP
+.B children_cond <SQL expression>
+Specifies a where-clause template used to form a children search condition
+(dn=".+,<dn>$").
+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 { YES | no }
+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
+meta-information, 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
+\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
+\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 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
+\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 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
+\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.
+
+.TP
+.B upper_func <SQL function name>
+Specifies the name of a function that converts a given value to uppercase.
+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 { NO | yes }
+Set this directive to
+.B yes
+if
+.B upper_func
+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 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
+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 "CONCAT(?,?)";
+a form that is known to be highly portable (IBM db2, PostgreSQL) is
+.BR "?||?",
+but an explicit cast may be required when operating on literal strings:
+.BR "CAST(?||? AS VARCHAR(<length>))".
+On some RDBMSes (IBM db2, MSSQL) the form
+.B "?+?"
+is known to work as well.
+Carefully check the documentation of your RDBMS or stay with the examples
+for supported ones.
+This is \fIexperimental\fP and may change in future releases.
+
+.TP
+.B aliasing_keyword <string>
+Define the aliasing keyword. Some RDBMSes use the word "\fIAS\fP"
+(the default), others don't use any.
+
+.TP
+.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 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 \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
+in ldap_oc_mappings, an
+.I add
+operation will fail regardless of the
+.B fail_if_no_mapping
+switch; see section "METAINFORMATION USED" for details.
+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.
+
+.TP
+.B autocommit { NO | yes }
+Activates autocommit; by default, it is off.
+
.SH METAINFORMATION USED
.LP
Almost everything mentioned later is illustrated in examples located
in the
-.B slapd/back-sql/rdbms_depend/
+.B servers/slapd/back\-sql/rdbms_depend/
directory in the OpenLDAP source tree, and contains scripts for
-generating sample database for Oracle,MS SQL Server and mySQL.
+generating sample database for Oracle, MS SQL Server, mySQL and more
+(including PostgreSQL and IBM db2).
.LP
-First thing that one must arrange for himself is what set of LDAP
+The first thing that one must arrange is what set of LDAP
object classes can present your RDBMS information.
.LP
-The easiest way is to create an objectclass for each entity you had in
+The easiest way is to create an objectClass for each entity you had in
ER-diagram when designing your relational schema.
Any relational schema, no matter how normalized it is, was designed
after some model of your application's domain (for instance, accounts,
It means that for every attribute of every such instance there is an
effective SQL query that loads its values.
.LP
-Also you might want your object classes to conform to some of standard
+Also you might want your object classes to conform to some of the standard
schemas like inetOrgPerson etc.
.LP
Nevertheless, when you think it out, we must define a way to translate
-LDAP operation requests to (series of) SQL queries.
+LDAP operation requests to (a series of) SQL queries.
Let us deal with the SEARCH operation.
.LP
Example:
organization in two tables:
.LP
.nf
- PERSONS PHONES
- ---------- -------------
- id integer id integer
- first_name varchar pers_id integer references persons(id)
- last_name varchar phone
+ PERSONS PHONES
+ ---------- -------------
+ id integer id integer
+ first_name varchar pers_id integer references persons(id)
+ last_name varchar phone
middle_name varchar
...
.fi
person
-------
MUST cn
- MAY telephoneNumber
- MAY firstName
- MAY lastName
+ MAY telephoneNumber $ firstName $ lastName
...
.fi
.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 this tables and arrange these values, we could
+attribute, how to join these tables and arrange these values, we could
try to automatically generate such statements, and translate search
filters to SQL WHERE clauses.
.LP
-To store such information, we add three more tables to our schema, so
-that and fill it with data (see samples):
+To store such information, we add three more tables to our schema
+and fill it with data (see samples):
.LP
.nf
ldap_oc_mappings (some columns are not listed for clarity)
.fi
.LP
This table defines a mapping between objectclass (its name held in the
-"name" column), and a table that holds primary key for corresponding
+"name" column), and a table that holds the primary key for corresponding
entities.
For instance, in our example, the person entity, which we are trying
to present as "person" objectclass, resides in two tables (persons and
-phones), and is identified by persons.id column (that we will call
-primary key for this entity).
+phones), and is identified by the persons.id column (that we will call
+the primary key for this entity).
Keytbl and keycol thus contain "persons" (name of the table), and "id"
(name of the column).
.LP
ldap_attr_mappings (some columns are not listed for clarity)
-----------
id=1
- oc_id=1
+ oc_map_id=1
name="cn"
sel_expr="CONCAT(persons.first_name,' ',persons.last_name)"
from_tbls="persons"
that load their values.
Note that, unlike LDAP schema, these are not
.B attribute types
-- attribute "cn" for "person" objectclass can well
-have its values in different table than "cn" for other objectclass,
+- the attribute "cn" for "person" objectclass can
+have its values in different tables than "cn" for some other objectclass,
so attribute mappings depend on objectclass mappings (unlike attribute
types in LDAP schema, which are indifferent to objectclasses).
Thus, we have oc_map_id column with link to oc_mappings table.
.LP
-Now we cut the SQL query that loads values for given attribute into 3 parts.
+Now we cut the SQL query that loads values for a given attribute into 3 parts.
First goes into sel_expr column - this is the expression we had
between SELECT and FROM keywords, which defines WHAT to load.
Next is table list - text between FROM and WHERE keywords.
-It may contain aliases for convenience (see exapmles).
-The last is part of where clause, which (if exists at all) express the
-condition for joining the table containing values wich table
-containing primary key (foreign key equality and such).
-If values are in the same table with primary key, then this column is
+It may contain aliases for convenience (see examples).
+The last is part of the where clause, which (if it exists at all) expresses the
+condition for joining the table containing values with the table
+containing the primary key (foreign key equality and such).
+If values are in the same table as the primary key, then this column is
left NULL (as for cn attribute above).
.LP
Having this information in parts, we are able to not only construct
queries that load attribute values by id of entry (for this we could
store SQL query as a whole), but to construct queries that load id's
-of objects that correspond to given search filter (or at least part of
+of objects that correspond to a given search filter (or at least part of
it).
See below for examples.
.LP
same table), which allows you to add any tree structure(s) to your
flat relational data.
Having id of objectclass mapping, we can determine table and column
-for primary key, and keyval stores value of it, thus defining exact
-tuple corresponding to LDAP entry with this DN.
+for primary key, and keyval stores value of it, thus defining the exact
+tuple corresponding to the LDAP entry with this DN.
.LP
Note that such design (see exact SQL table creation query) implies one
-important constraint - the key must be integer.
-But all that I know about well-designed schemas makes me think that it
-s not very narrow ;) If anyone needs support for different types for
+important constraint - the key must be an integer.
+But all that I know about well-designed schemas makes me think that it's
+not very narrow ;) If anyone needs support for different types for
keys - he may want to write a patch, and submit it to OpenLDAP ITS,
then I'll include it.
.LP
-Also, several people complained that they don't really need very
-structured tree, and they don't want to update one more table every
-time they add or delete instance in relational schema.
-Those can use a view instead of real table for ldap_entries, something
+Also, several users complained that they don't really need very
+structured trees, and they don't want to update one more table every
+time they add or delete an instance in the relational schema.
+Those people can use a view instead of a real table for ldap_entries, something
like this (by Robin Elfrink):
.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
-.SH Typical SQL backend operation
-Having metainformation loaded, the SQL backend uses these tables to
+
+.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 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.
.LP
Example:
-for our query with filter (telephoneNumber=123*) we would get following
+for our query with filter (telephoneNumber=123*) we would get the following
query generated (which loads candidate IDs)
.LP
.nf
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)
or "... AND dn=?" (for BASE search)
or "... AND dn LIKE '%?'" (for SUBTREE)
.LP
-Then, for each candidate, we load attributes requested using
+Then, for each candidate, we load the requested attributes using
per-attribute queries like
.LP
.nf
WHERE persons.id=? AND phones.pers_id=persons.id
.fi
.LP
-Then, we use test_filter() from frontend API to test entry for full
+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 most relaxed SQL condition to filter candidates), and send it to
-user.
+into the most relaxed SQL condition to filter candidates), and send it to
+the user.
.LP
-ADD, DELETE, MODIFY operations also performed on per-attribute
-metainformation (add_proc etc.).
+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 value of given attribute, using
-given entry keyval (see examples -- mostly ORACLE and MSSQL - since
-there're no stored procs in mySQL).
+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).
.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 order of parameters passed to those statements.
+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, lets remember that among other major differences to
-complete LDAP data model, the concept above does not directly support
-such things as multiple objectclasses for entry, and referrals.
+.SH COMMON TECHNIQUES
+First of all, let's recall that among other major differences to the
+complete LDAP data model, the above illustrated concept does not directly
+support such features 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 schema -
-ldap_entry_objectclasses(entry_id,oc_name), and
-ldap_referrals(entry_id,url).
-.LP
-First contains any number of objectclass names that corresponding
-entries will be found by, in addition to that mentioned in
-mapping.
-The SQL backend automatically adds attribute mapping for "objectclass"
-attribute to each objectclass mapping, that loads values from this table.
-So, you may, for instance, have mapping for inetOrgPerson, and use it
+The SQL backend requires that one more table is added to the schema:
+ldap_entry_objectclasses(entry_id,oc_name).
+.LP
+That table contains any number of objectclass names that corresponding
+entries will possess, in addition to that mentioned in mapping.
+The SQL backend automatically adds attribute mapping for the "objectclass"
+attribute to each objectclass mapping that loads values from this table.
+So, you may, for instance, have a mapping for inetOrgPerson, and use it
for queries for "person" objectclass...
.LP
-Second table contains any number of referrals associated with 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 referral, as
-described in Administrators Guide.
-.LP
+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 \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 (brain-dead?) filter
+of the form
+\fB(!(hasSubordinates=TRUE))\fP
+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 mean spaces, ASCII 0x20 char) 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 through back-sql, the prettified
+values are actually used instead.
+
+.LP
+.SH BUGS
+When the
+.B ldap_entry_objclasses
+table is empty, filters on the
+.B objectClass
+attribute erroneously result in no candidates.
+A workaround consists in adding at least one row to that table,
+no matter if valid or not.
+
+.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/
-direcetory in the OpenLDAP source tree.
+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
.SH SEE ALSO
.BR slapd.conf (5),
.BR slapd (8).
projects / openldap / blobdiff