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.. _sql-ext:
SQLite Interface
================
Log analysis in **lnav** can be done using the SQLite interface. Log messages
can be accessed via `virtual tables <https://www.sqlite.org/vtab.html>`_ that
are created for each file format. The tables have the same name as the log
format and each message is its own row in the table. For example, given the
following log message from an Apache access log::
127.0.0.1 - frank [10/Oct/2000:13:55:36 -0700] "GET /apache_pb.gif HTTP/1.0" 200 2326
These columns would be available for its row in the :code:`access_log` table:
.. csv-table::
:class: query-results
:header-rows: 1
log_line,log_part,log_time,log_idle_msecs,log_level,log_mark,log_comment,log_tags,log_filters,c_ip,cs_method,cs_referer,cs_uri_query,cs_uri_stem,cs_user_agent,cs_username,cs_version,sc_bytes,sc_status
0,<NULL>,2000-10-10 13:55:36.000,0,info,1,<NULL>,<NULL>,<NULL>,127.0.0.1,GET,<NULL>,<NULL>,/apache_pb.gif,<NULL>,frank,HTTP/1.0,2326,200
.. note:: Some columns are hidden by default to reduce the amount of noise in
results, but they can still be accessed when explicitly used. The hidden
columns are: :code:`log_path`, :code:`log_text`, :code:`log_body`, and
:code:`log_raw_text`.
You can activate the SQL prompt by pressing the :kbd:`;` key. At the
prompt, you can start typing in the desired SQL statement and/or double-tap
:kbd:`TAB` to activate auto-completion. A help window will appear above
the prompt to guide you in the usage of SQL keywords and functions.
.. figure:: sql-help.png
:align: center
Screenshot of the online help for the SQL prompt.
.. figure:: group_concat-help.png
:align: center
Screenshot of the online help for the :code:`group_concat()` function.
A simple query to perform on an Apache access log might be to get the average
and maximum number of bytes returned by the server, grouped by IP address:
.. code-block:: custsqlite
;SELECT c_ip, avg(sc_bytes), max(sc_bytes) FROM access_log GROUP BY c_ip
After pressing :kbd:`Enter`, SQLite will execute the query using **lnav**'s
virtual table implementation to extract the data directly from the log files.
Once the query has finished, the main window will switch to the DB view to
show the results. Press :kbd:`q` to return to the log view and press :kbd:`v`
to return to the log view. If the SQL results contain a
:code:`log_line` column, you can press to :kbd:`Shift` + :kbd:`V` to
switch between the DB view and the log
.. figure:: query-results.png
:align: center
Screenshot of the SQL results view.
The DB view has the following display features:
* Column headers stick to the top of the view when scrolling.
* A stacked bar chart of the numeric column values is displayed underneath the
rows. Pressing :kbd:`TAB` will cycle through displaying no columns, each
individual column, or all columns.
* JSON columns in the top row can be pretty-printed by pressing :kbd:`p`.
The display will show the value and JSON-Pointer path that can be passed to
the `jget`_ function.
Log Tables
----------
Each log format has its own database table that can be used to access log
messages that match that format. The table name is the same as the format
name, for example, the :code:`syslog_log` format will have a table that is
also named :code:`syslog_log`. There is also an :code:`all_logs` table
that provides access to all messages from all formats.
.. note:: Only the displayed log messages are reflected in the SQLite
interface. Any log messages that have been filtered out are not
accessible.
The columns in the log tables are made up of several builtins along with
the values captured by the log format specification. Use the :code:`.schema`
command in the SQL prompt to examine a dump of the current database schema.
The following columns are builtin and included in a :code:`SELECT *`:
:log_line: The line number for the message in the log view.
:log_part: The partition the message is in. This column can be changed by
an :code:`UPDATE` or the :ref:`:parition-name<partition_name>` command.
:log_time: The adjusted timestamp for the log message. This time can differ
from the log message's time stamp if it arrived out-of-order and the log
format expects log files to be time-ordered.
:log_actual_time: The log messages original timestamp in the file.
:log_idle_msecs: The difference in time between this messages and the
previous. The unit of time is milliseconds.
:log_level: The log message level.
:log_mark: True if the log message was marked by the user.
:log_comment: The comment for the message. This column can be changed by
an :code:`UPDATE` or the :ref:`:comment<comment>` command.
:log_tags: A JSON list of tags for the message. This column can be changed
by an :code:`UPDATE` or the :ref:`:tag<tag>` command.
:log_filters: A JSON list of filter IDs that matched this message
The following columns are builtin and are hidden, so they will *not* be
included in a :code:`SELECT *`:
:log_time_msecs: The adjusted timestamp for the log message as the number of
milliseconds from the epoch. This column can be more efficient to use for
time-related operations, like :ref:`timeslice()<timeslice>`.
:log_path: The path to the log file this message is from.
:log_text: The full text of the log message.
:log_body: The body of the log message.
:log_raw_text: The raw text of this message from the log file. In this case
of JSON and CSV logs, this will be the exact line of JSON-Line and CSV
text from the file.
Extensions
----------
To make it easier to analyze log data from within **lnav**, there are several
built-in extensions that provide extra functions and collators beyond those
`provided by SQLite <http://www.sqlite.org/lang_corefunc.html>`_. The majority
of the functions are from the
`extensions-functions.c <http://www.sqlite.org/contrib>`_ file available from
the `sqlite.org <http://sqlite.org>`_ web site.
.. tip:: You can include a SQLite database file on the command-line and use
**lnav**'s interface to perform queries. The database will be attached with
a name based on the database file name.
Commands
--------
A SQL command is an internal macro implemented by lnav.
* .schema - Open the schema view. This view contains a dump of the schema
for the internal tables and any tables in attached databases.
* .msgformats - Executes a canned query that groups and counts log messages by
the format of their message bodies. This command can be useful for quickly
finding out the types of messages that are most common in a log file.
Variables
---------
The following variables are available in SQL statements:
* $LINES - The number of lines in the terminal window.
* $COLS - The number of columns in the terminal window.
Environment
-----------
Environment variables can be accessed in queries using the usual syntax of
:code:`$VAR_NAME`. For example, to read the value of the "USER" variable, you
can write:
.. code-block:: custsqlite
;SELECT $USER
.. _collators:
Collators
---------
* **naturalcase** - Compare strings "naturally" so that number values in the
string are compared based on their numeric value and not their character
values. For example, "foo10" would be considered greater than "foo2".
* **naturalnocase** - The same as naturalcase, but case-insensitive.
* **ipaddress** - Compare IPv4/IPv6 addresses.
Reference
---------
The following is a reference of the SQL syntax and functions that are available:
.. include:: ../../src/internals/sql-ref.rst
|
