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Date: Mon, 20 May 2019 14:37:20 +0300 From: Adrian Hunter <adrian.hunter@...el.com> To: Arnaldo Carvalho de Melo <acme@...nel.org> Cc: Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org Subject: [PATCH 14/22] perf db-export: Add brief documentation Add brief documentation to explain how the database export maintains backward and forward compatibility. Signed-off-by: Adrian Hunter <adrian.hunter@...el.com> --- tools/perf/Documentation/db-export.txt | 41 ++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 tools/perf/Documentation/db-export.txt diff --git a/tools/perf/Documentation/db-export.txt b/tools/perf/Documentation/db-export.txt new file mode 100644 index 000000000000..52ffccb02d55 --- /dev/null +++ b/tools/perf/Documentation/db-export.txt @@ -0,0 +1,41 @@ +Database Export +=============== + +perf tool's python scripting engine: + + tools/perf/util/scripting-engines/trace-event-python.c + +supports scripts: + + tools/perf/scripts/python/export-to-sqlite.py + tools/perf/scripts/python/export-to-postgresql.py + +which export data to a SQLite3 or PostgreSQL database. + +The export process provides records with unique sequential ids which allows the +data to be imported directly to a database and provides the relationships +between tables. + +Over time it is possible to continue to expand the export while maintaining +backward and forward compatibility, by following some simple rules: + +1. Because of the nature of SQL, existing tables and columns can continue to be +used so long as the names and meanings (and to some extent data types) remain +the same. + +2. New tables and columns can be added, without affecting existing SQL queries, +so long as the new names are unique. + +3. Scripts that use a database (e.g. exported-sql-viewer.py) can maintain +backward compatibility by testing for the presence of new tables and columns +before using them. e.g. function IsSelectable() in exported-sql-viewer.py + +4. The export scripts themselves maintain forward compatibility (i.e. an existing +script will continue to work with new versions of perf) by accepting a variable +number of arguments (e.g. def call_return_table(*x)) i.e. perf can pass more +arguments which old scripts will ignore. + +5. The scripting engine tests for the existence of script handler functions +before calling them. The scripting engine can also test for the support of new +or optional features by checking for the existence and value of script global +variables. -- 2.17.1
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