Difference between revisions of "Understanding database timelines in Lianja"

Revision as of 09:04, 30 September 2016

See Also

Category:Database Timelines

What are Database Timelines?

Database timelines provide row versioning for Lianja database tables. Whenever a change is made to a table that is timeline enabled then delta changes are automatically recorded for each transaction. Changes made to any tables that are timeline enabled can be undone much like you would undo changes to program code that you edit in a text editor.

Using Database Timelines

To enable database timelines all you need to do is issue the set timeline on command in your Lianja configuration file.

set timeline on

Timelines can be enabled on a per App basis using the Timelines Enabled setting in the App Settings. Individual sections also have a Timelines Enabled attribute in their Attributes. The Timelines Enabled App Setting must be checked (True) for the section Timelines Enabled attribute to be applied.

Viewing a timeline

There are 2 ways to view a timeline.

• The list timeline command
• The select * from systimeline SQL command

list timeline [range <begin as string-date> [, <end as string-date>]] [for <condition as logical>] [to file <filename as character>]

To view a timeline for a particular table e.g.

list timeline for table = "customers"

To view a timeline since a certain date use the range keyword. Notice that the date range is encoded as a string in the format "YYYYMMDDHH:MM:SS:". This can be abbreviated e.g.

// list the timeline since 1st October 2009
list timeline range "20091001" 

// list the timeline between the 1st and 7th of October 2009 
list timeline range "20091001","20091007" 

SQL SELECT can be used with the Lianja Data Object functions (rdo_xxx() functions) to traverse the timeline and generate html if required e.g.

echo "Timeline report<br>"
results = rdo_query("SELECT * FROM systimeline WHERE between(timestamp, '20091001', '20091007')")
foreach results as row
    echo "Table " + row["TABLE"] + " changed by " + row["USER"] + " on " + row["TIMESTAMP"]
    echo ", command was " + row["COMMAND"] + "<br>"
endfor
results = null

Undoing database changes

You can undo database changes with the rollback timeline command. The range and for clauses can also be specified in the same way as the list timeline command e.g.

rollback timeline [range <begin as string-date> [, <end as string-date>]] [for <condition as logical>]

Clearing a timeline

The clear timeline command will reset a timeline.

clear timeline