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1Database Export2===============3 4perf tool's python scripting engine:5 6 tools/perf/util/scripting-engines/trace-event-python.c7 8supports scripts:9 10 tools/perf/scripts/python/export-to-sqlite.py11 tools/perf/scripts/python/export-to-postgresql.py12 13which export data to a SQLite3 or PostgreSQL database.14 15The export process provides records with unique sequential ids which allows the16data to be imported directly to a database and provides the relationships17between tables.18 19Over time it is possible to continue to expand the export while maintaining20backward and forward compatibility, by following some simple rules:21 221. Because of the nature of SQL, existing tables and columns can continue to be23used so long as the names and meanings (and to some extent data types) remain24the same.25 262. New tables and columns can be added, without affecting existing SQL queries,27so long as the new names are unique.28 293. Scripts that use a database (e.g. exported-sql-viewer.py) can maintain30backward compatibility by testing for the presence of new tables and columns31before using them. e.g. function IsSelectable() in exported-sql-viewer.py32 334. The export scripts themselves maintain forward compatibility (i.e. an existing34script will continue to work with new versions of perf) by accepting a variable35number of arguments (e.g. def call_return_table(*x)) i.e. perf can pass more36arguments which old scripts will ignore.37 385. The scripting engine tests for the existence of script handler functions39before calling them. The scripting engine can also test for the support of new40or optional features by checking for the existence and value of script global41variables.42