16.17.9. Dump and Reload Graphs
Why?
Every DBMS needs to offer a mechanism for bulk export and import of data.
Virtuoso supports dumping and reloading graph model data (e.g., RDF), as well as relational data (e.g., SQL) (discussed elsewhere).
How?
We have created stored procedures for the task. The dump procedures leverage SPARQL to facilitate selective data dump(s) from one or more Named Graphs, each denoted by an IRI.
Dump One Graph
The procedure dump_one_graph can be used to dump any single Named Graph.
Parameters
-
IN
srcgraph
VARCHAR -- source graph
-
IN
out_file
VARCHAR -- output file
-
IN
file_length_limit
INTEGER -- maximum length of dump files
Procedure source
CREATE PROCEDURE dump_one_graph
( IN srcgraph VARCHAR
, IN out_file VARCHAR
, IN file_length_limit INTEGER := 1000000000
)
{
DECLARE file_name VARCHAR;
DECLARE env, ses ANY;
DECLARE ses_len
, max_ses_len
, file_len
, file_idx INTEGER;
SET ISOLATION = 'uncommitted';
max_ses_len := 10000000;
file_len := 0;
file_idx := 1;
file_name := sprintf ('%s%06d.ttl', out_file, file_idx);
string_to_file ( file_name || '.graph',
srcgraph,
-2
);
string_to_file ( file_name,
sprintf ( '# Dump of graph <%s>, as of %s\n@base <> .\n',
srcgraph,
CAST (NOW() AS VARCHAR)
),
-2
);
env := vector (dict_new (16000), 0, '', '', '', 0, 0, 0, 0, 0);
ses := string_output ();
FOR (SELECT * FROM ( SPARQL DEFINE input:storage ""
SELECT ?s ?p ?o { GRAPH `iri(?:srcgraph)` { ?s ?p ?o } }
) AS sub OPTION (LOOP)) DO
{
http_ttl_triple (env, "s", "p", "o", ses);
ses_len := length (ses);
IF (ses_len > max_ses_len)
{
file_len := file_len + ses_len;
IF (file_len > file_length_limit)
{
http (' .\n', ses);
string_to_file (file_name, ses, -1);
gz_compress_file (file_name, file_name||'.gz');
file_delete (file_name);
file_len := 0;
file_idx := file_idx + 1;
file_name := sprintf ('%s%06d.ttl', out_file, file_idx);
string_to_file ( file_name,
sprintf ( '# Dump of graph <%s>, as of %s (part %d)\n@base <> .\n',
srcgraph,
CAST (NOW() AS VARCHAR),
file_idx),
-2
);
env := VECTOR (dict_new (16000), 0, '', '', '', 0, 0, 0, 0, 0);
}
ELSE
string_to_file (file_name, ses, -1);
ses := string_output ();
}
}
IF (LENGTH (ses))
{
http (' .\n', ses);
string_to_file (file_name, ses, -1);
gz_compress_file (file_name, file_name||'.gz');
file_delete (file_name);
}
}
;
To load the procedure into Virtuoso, it can simply be copied and pasted into the Virtuoso isql command line tool or Interactive SQL UI of the Conductor and executed.
Example
Call the dump_one_graph procedure with appropriate arguments:
$ pwd
/Applications/OpenLink Virtuoso/Virtuoso 6.1/database
$ grep DirsAllowed virtuoso.ini
DirsAllowed = ., ../vad,
$ /opt/virtuoso/bin/isql 1111
Connected to OpenLink Virtuoso
Driver: 06.01.3127 OpenLink Virtuoso ODBC Driver
OpenLink Interactive SQL (Virtuoso), version 0.9849b.
Type HELP; for help and EXIT; to exit.
SQL> dump_one_graph ('http://daas.openlinksw.com/data#', './data_', 1000000000);
Done. -- 1438 msec.
$
As a result, a dump of the graph <http://daas.openlinksw.com/data#> will be found in the files data_XX (located in your Virtuoso db folder):
$ ls
data_000001.ttl
data_000002.ttl
....
data_000001.ttl.graph
Dump Multiple Graphs
The dump_graphs procedure can be used to dump all the graphs in a Virtuoso server to a set of turtle (.ttl) data files in the specified dump directory.
Parameters
The procedure dump_graphs has the following parameters:
-
IN
dir
VARCHAR -- dump directory
-
IN
file_length_limit
INTEGER -- maximum length of dump files
Note: The dump directory must be included in the DirsAllowed parameter of the Virtuoso configuration file (virtuoso.ini), or the Virtuoso server will not be able to create or access the data files.
Source
The procedure dump_graphs has the following source:
CREATE PROCEDURE dump_graphs
( IN dir VARCHAR := 'dumps' ,
IN file_length_limit INTEGER := 1000000000
)
{
DECLARE inx INT;
inx := 1;
SET ISOLATION = 'uncommitted';
FOR ( SELECT *
FROM ( SPARQL DEFINE input:storage ""
SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } .
FILTER ( ?g != virtrdf: )
}
) AS sub OPTION ( LOOP )) DO
{
dump_one_graph ( "g",
sprintf ('%s/graph%06d_', dir, inx),
file_length_limit
);
inx := inx + 1;
}
}
;
Example
-
Call the
dump_graphs
procedure:
$ pwd /Applications/OpenLink Virtuoso/Virtuoso 6.1/database $ grep DirsAllowed virtuoso.ini DirsAllowed = ., ../vad, ./dumps $ /opt/virtuoso/bin/isql 1111 Connected to OpenLink Virtuoso Driver: 06.01.3127 OpenLink Virtuoso ODBC Driver OpenLink Interactive SQL (Virtuoso), version 0.9849b. Type HELP; for help and EXIT; to exit. SQL> dump_graphs(); Done. -- 998 msec. SQL> quit;
-
As a result, a dump of the graph will be found in the files dumps/data_XX (located in your Virtuoso db folder):
<verbatim> $ ls dumps graph000001_000001.ttl graph000005_000001.ttl graph000001_000001.ttl.graph graph000005_000001.ttl.graph graph000002_000001.ttl graph000006_000001.ttl graph000002_000001.ttl.graph graph000006_000001.ttl.graph graph000003_000001.ttl graph000007_000001.ttl graph000003_000001.ttl.graph graph000007_000001.ttl.graph graph000004_000001.ttl graph000008_000001.ttl graph000004_000001.ttl.graph graph000008_000001.ttl.graph
Load Graphs
The stored procedure load_graphs procedure performs a bulk load from a file.
Parameters
The procedure load_graphs has the following parameters:
-
IN
dir
VARCHAR -- dump directory
Note: The dump directory must be included in the DirsAllowed parameter of the Virtuoso configuration file (virtuoso.ini), or the Virtuoso server will not be able to create or access the data files.
Source
The procedure load_graphs has the following source:
CREATE PROCEDURE load_graphs
( IN dir VARCHAR := 'dumps/' )
{
DECLARE arr ANY;
DECLARE g VARCHAR;
arr := sys_dirlist (dir, 1);
log_enable (2, 1);
FOREACH (VARCHAR f IN arr) DO
{
IF (f LIKE '*.ttl')
{
DECLARE CONTINUE HANDLER FOR SQLSTATE '*'
{
log_message (sprintf ('Error in %s', f));
};
g := file_to_string (dir || '/' || f || '.graph');
DB.DBA.TTLP_MT (file_open (dir || '/' || f), g, g, 255);
}
}
EXEC ('CHECKPOINT');
}
;
Example
$ /opt/virtuoso/bin/isql 1112 Connected to OpenLink Virtuoso Driver: 06.01.3127 OpenLink Virtuoso ODBC Driver OpenLink Interactive SQL (Virtuoso), version 0.9849b. Type HELP; for help and EXIT; to exit. SQL> load_graphs(); Done. -- 2392 msec. SQL>