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.\" ========================================================================
.\"
.IX Title "RDF::Query::Compiler::SQL 3pm"
.TH RDF::Query::Compiler::SQL 3pm "2012-01-31" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
RDF::Query::Compiler::SQL \- Compile a SPARQL query directly to SQL.
.SH "VERSION"
.IX Header "VERSION"
This document describes RDF::Query::Compiler::SQL version 2.908.
.SH "METHODS"
.IX Header "METHODS"
.ie n .IP """new ( $parse_tree )""" 4
.el .IP "\f(CWnew ( $parse_tree )\fR" 4
.IX Item "new ( $parse_tree )"
Returns a new compiler object.
.ie n .IP """compile ()""" 4
.el .IP "\f(CWcompile ()\fR" 4
.IX Item "compile ()"
Returns a \s-1SQL\s0 query string for the specified parse tree.
.ie n .IP """emit_select""" 4
.el .IP "\f(CWemit_select\fR" 4
.IX Item "emit_select"
Returns a \s-1SQL\s0 query string representing the query.
.ie n .IP """limit_clause""" 4
.el .IP "\f(CWlimit_clause\fR" 4
.IX Item "limit_clause"
Returns a \s-1SQL\s0 \s-1LIMIT\s0 clause, or an empty string if the query does not need limiting.
.ie n .IP """order_by_clause""" 4
.el .IP "\f(CWorder_by_clause\fR" 4
.IX Item "order_by_clause"
Returns a \s-1SQL\s0 \s-1ORDER\s0 \s-1BY\s0 clause, or an empty string if the query does not use ordering.
.ie n .IP """variable_columns ( $var )""" 4
.el .IP "\f(CWvariable_columns ( $var )\fR" 4
.IX Item "variable_columns ( $var )"
Given a variable name, returns the set of column aliases that store the values
for the column (values for Literals, URIs, and Blank Nodes).
.ie n .IP """add_variable_values_joins""" 4
.el .IP "\f(CWadd_variable_values_joins\fR" 4
.IX Item "add_variable_values_joins"
Modifies the query by adding \s-1LEFT\s0 JOINs to the tables in the database that
contain the node values (for literals, resources, and blank nodes).
.ie n .IP """patterns2sql ( \e@triples, \e$level, %args )""" 4
.el .IP "\f(CWpatterns2sql ( \e@triples, \e$level, %args )\fR" 4
.IX Item "patterns2sql ( @triples, $level, %args )"
Builds the \s-1SQL\s0 query in instance data from the supplied \f(CW@triples\fR.
\&\f(CW$level\fR is used as a unique identifier for recursive calls.
.Sp
\&\f(CW%args\fR may contain callback closures for the following keys:
.Sp
.Vb 2
\&  \*(Aqwhere_hook\*(Aq
\&  \*(Aqfrom_hook\*(Aq
.Ve
.Sp
When present, these closures are used to add \s-1SQL\s0 \s-1FROM\s0 and \s-1WHERE\s0 clauses
to the query instead of adding them directly to the object's instance data.
.ie n .IP """expr2sql ( $expression, \e$level, %args )""" 4
.el .IP "\f(CWexpr2sql ( $expression, \e$level, %args )\fR" 4
.IX Item "expr2sql ( $expression, $level, %args )"
Returns a \s-1SQL\s0 expression for the supplied query \f(CW$expression\fR.
\&\f(CW$level\fR is used as a unique identifier for recursive calls.
.Sp
\&\f(CW%args\fR may contain callback closures for the following keys:
.Sp
.Vb 2
\&  \*(Aqwhere_hook\*(Aq
\&  \*(Aqfrom_hook\*(Aq
.Ve
.Sp
When present, these closures are used to add necessary \s-1SQL\s0 \s-1FROM\s0 and \s-1WHERE\s0
clauses to the query.
.ie n .IP """_mysql_hash ( $data )""" 4
.el .IP "\f(CW_mysql_hash ( $data )\fR" 4
.IX Item "_mysql_hash ( $data )"
Returns a hash value for the supplied \f(CW$data\fR string. This value is computed
using the same algorithm that Redland's mysql storage backend uses.
.ie n .IP """_mysql_node_hash ( $node )""" 4
.el .IP "\f(CW_mysql_node_hash ( $node )\fR" 4
.IX Item "_mysql_node_hash ( $node )"
Returns a hash value (computed by \f(CW\*(C`_mysql_hash\*(C'\fR for the supplied \f(CW$node\fR.
The hash value is based on the string value of the node and the node type.
.ie n .IP """qualify_uri ( $uri )""" 4
.el .IP "\f(CWqualify_uri ( $uri )\fR" 4
.IX Item "qualify_uri ( $uri )"
Returns a fully qualified \s-1URI\s0 from the supplied \f(CW$uri\fR. \f(CW$uri\fR may already
be a qualified \s-1URI\s0, or a parse tree for a qualified \s-1URI\s0 or QName. If \f(CW$uri\fR is
a QName, the namespaces defined in the query parse tree are used to fully qualify.
.ie n .IP """add_function ( $uri, $function )""" 4
.el .IP "\f(CWadd_function ( $uri, $function )\fR" 4
.IX Item "add_function ( $uri, $function )"
Associates the custom function \f(CW$function\fR (a \s-1CODE\s0 reference) with the
specified \s-1URI\s0, allowing the function to be called by query FILTERs.
.ie n .IP """get_function ( $uri )""" 4
.el .IP "\f(CWget_function ( $uri )\fR" 4
.IX Item "get_function ( $uri )"
If \f(CW$uri\fR is associated with a query function, returns a \s-1CODE\s0 reference
to the function. Otherwise returns \f(CW\*(C`undef\*(C'\fR.
.SH "AUTHOR"
.IX Header "AUTHOR"
.Vb 1
\& Gregory Williams <gwilliams@cpan.org>
.Ve