1Database Export 2=============== 3 4perf tool's python scripting engine: 5 6 tools/perf/util/scripting-engines/trace-event-python.c 7 8supports scripts: 9 10 tools/perf/scripts/python/export-to-sqlite.py 11 tools/perf/scripts/python/export-to-postgresql.py 12 13which export data to a SQLite3 or PostgreSQL database. 14 15The export process provides records with unique sequential ids which allows the 16data to be imported directly to a database and provides the relationships 17between tables. 18 19Over time it is possible to continue to expand the export while maintaining 20backward and forward compatibility, by following some simple rules: 21 221. Because of the nature of SQL, existing tables and columns can continue to be 23used so long as the names and meanings (and to some extent data types) remain 24the 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 maintain 30backward compatibility by testing for the presence of new tables and columns 31before using them. e.g. function IsSelectable() in exported-sql-viewer.py 32 334. The export scripts themselves maintain forward compatibility (i.e. an existing 34script will continue to work with new versions of perf) by accepting a variable 35number of arguments (e.g. def call_return_table(*x)) i.e. perf can pass more 36arguments which old scripts will ignore. 37 385. The scripting engine tests for the existence of script handler functions 39before calling them. The scripting engine can also test for the support of new 40or optional features by checking for the existence and value of script global 41variables. 42