Introduction
In this blog a script is introduced to export a SAP HANA Graph workspace into the dot language.
SAP HANA Graph
SAP HANA Graph is part of the SAP HANA core. It adds native support for graph processing to SAP HANA with own objects and language (GraphScript). A graph is based on two tables, one for the nodes and one for the edges. Both are combined in a so-called graph workspace.
For a deeper understanding please refer to
this blog.
GraphViz & The Dot Language
GraphViz is a software to visualize graphs. To describe these graphs the DOT language is used. The final visualization can be calculated by a variant of algorithms like
dot or
neato.
Idea & Solution
SAP HANA Graph allows to view a graph with its own graph viewer. Beside this, it's possible to export the graph objects (base tables, etc.). A conversion to a graph format like dot is currently not supported. This can be helpful to visualize the data with other tools, algorithms and parameters. In addition, sharing is much easier.
The script introduced in this blog allows the user to export SAP HANA graphs into a dot file. It queries the
GRAPH_WORKSPACES system view to get all needed metadata. Using this metadata it knows which tables are used by the graph workspace and their relation to each other and can generate the dot file.
In SAP HANA it's possible to add additional attributes to a node and to an edge by adding columns to the base table. These columns can be queried in GraphScript procedures. To include them as well, all columns are stored in a special attribute called
__custom_attributes as key-value pairs, both wrapped in single quotes. They aren't included directly as attributes to avoid naming conflict with predefined dot-attributes. Please refer the "Example output" section for an example.
Usage
The script is written in Python and can be found in
this GitHub repository. Python 2.7 is needed to use it.
Command line
The script can be used from the command line with the following mandatory parameters:
Parameter short |
Parameter long |
Description |
dh |
db_host |
Host of the SAP HANA database |
dp |
db_port |
SQL port of the SAP HANA database |
du |
db_user |
Database user with access to the graph workspace |
dpw |
db_password |
Password of the database user |
dws |
db_workspace_schema |
Graph workspace schema name |
dwn |
db_workspace_name |
Graph workspace name |
f |
file |
Output file |
python graph_export.py -dh host -dp 12345 -du user -dpw password -dws schema -dwn workspace -f out.dot
In python
Beside the command line, the export functionality can be used directly in python:
export = DotExport(user=user, password=password, host=host, port=port, workspace_name=workspace_name, workspace_schema_name=workspace_schema_name)
export.export(file_path=file_path)
export.close()
Example output
The following is a part from the export of the
Greek Mythology Graph Example used in the
SAP HANA Graph Reference:
strict digraph {
node_0 [label="Chaos", __custom_attributes="'NAME'='Chaos', 'TYPE'='primordial deity', 'RESIDENCE'='None'"]
node_1 [label="Gaia", __custom_attributes="'NAME'='Gaia', 'TYPE'='primordial deity', 'RESIDENCE'='None'"]
node_0 -> node_1 [__custom_attributes="'KEY'='1', 'SOURCE'='Chaos', 'TARGET'='Gaia', 'TYPE'='hasDaughter'"]
}
All columns and their values including the ones, which are not used by the graph workspace (e.g.
TYPE) are stored in the
__custom_attributes attribute.
Resources
