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ReStructuredText
194 lines
6.8 KiB
ReStructuredText
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.. _sql-ext:
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SQLite Extensions Reference
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===========================
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To make it easier to analyze log data from within **lnav**, there are several
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built-in extensions that provide extra functions and collators beyond those
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`provided by SQLite <http://www.sqlite.org/lang_corefunc.html>`_. The majority
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of the functions are from the
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`extensions-functions.c <http://www.sqlite.org/contrib>`_ file available from
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the `sqlite.org <http://sqlite.org>`_ web site.
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*Tip*: You can include a SQLite database file on the command-line and use
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**lnav**'s interface to perform queries. The database will be attached with
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a name based on the database file name.
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Commands
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--------
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A SQL command is an internal macro implemented by lnav.
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* .schema - Open the schema view. This view contains a dump of the schema
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for the internal tables and any tables in attached databases.
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Environment
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-----------
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Environment variables can be accessed in queries using the usual syntax of
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"$VAR_NAME". For example, to read the value of the "USER" variable, you can
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write:
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;SELECT $USER;
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Math
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----
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Basic mathematical functions:
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* cos(n)
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* sin(n)
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* tan(n)
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* cot(n)
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* cosh(n)
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* sinh(n)
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* coth(n)
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* acos(n)
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* asin(n)
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* atan(r1,r2)
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* atan2(r1,r2)
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* exp(n)
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* log(n)
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* log10(n)
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* power(x,y)
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* sign(n) - Return one of 3 possibilities +1,0 or -1 when the argument is
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respectively positive, 0 or negative.
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* sqrt(n)
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* square(n)
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* ceil(n)
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* floor(n)
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* pi()
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* degrees - Convert radians to degrees
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* radians - Convert degrees to radians
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Aggregate functions:
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* stddev
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* variance
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* mode
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* median
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* lower_quartile
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* upper_quartile
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String
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------
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Additional string comparison and manipulation functions:
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* difference(s1,s2) - Computes the number of different characters between the
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soundex value fo 2 strings.
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* replicate(s,n) - Given a string (s) in the first argument and an integer (n)
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in the second returns the string that constains s contatenated n times.
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* proper(s) - Ensures that the words in the given string have their first
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letter capitalized and the following letters are lower case.
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* charindex(s1,s2), charindex(s1,s2,n) - Given 2 input strings (s1,s2) and an
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integer (n) searches from the nth character for the string s1. Returns the
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position where the match occured. Characters are counted from 1. 0 is
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returned when no match occurs.
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* leftstr(s,n) - Given a string (s) and an integer (n) returns the n leftmost
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(UTF-8) characters if the string has a length<=n or is NULL this function is
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NOP.
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* rightstr(s,n) - Given a string (s) and an integer (n) returns the n rightmost
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(UTF-8) characters if the string has a length<=n or is NULL this function is
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NOP
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* reverse(s) - Given a string returns the same string but with the characters
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in reverse order.
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* padl(s,n) - Given an input string (s) and an integer (n) adds spaces at the
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beginning of (s) until it has a length of n characters. When s has a length
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>=n it's a NOP. padl(NULL) = NULL
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* padr(s,n) - Given an input string (s) and an integer (n) appends spaces at
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the end of s until it has a length of n characters. When s has a length >=n
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it's a NOP. padr(NULL) = NULL
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* padc(s,n) - Given an input string (s) and an integer (n) appends spaces at
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the end of s and adds spaces at the begining of s until it has a length of n
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characters. Tries to add has many characters at the left as at the right.
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When s has a length >=n it's a NOP. padc(NULL) = NULL
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* strfilter(s1,s2) - Given 2 string (s1,s2) returns the string s1 with the
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characters NOT in s2 removed assumes strings are UTF-8 encoded.
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* regexp(re,s) - Return 1 if the regular expression 're' matches the given
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string.
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* regexp_replace(str, re, repl) - Replace the portions of the given string
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that match the regular expression with the replacement string. **NOTE**:
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The arguments for the string and the regular expression in this function are
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reversed from the plain regexp() function. This is to be somewhat compatible
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with functions in other database implementations.
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* startswith(s1,prefix) - Given a string and prefix, return 1 if the string
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starts with the given prefix.
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* endswith(s1,suffix) - Given a string and suffix, return 1 if the string ends
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with the given suffix.
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* regexp_match(re,str) - Match and extract values from a string using a regular
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expression. The "re" argument should be a PCRE with captures. If there is
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a single capture, that captured value will be directly returned. If there
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is more than one capture, a JSON object will be returned with field names
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matching the named capture groups or 'col_N' where 'N' is the index of the
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capture. If the expression does not match the string, NULL is returned.
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* extract(str) - Parse and extract values from a string using the same
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algorithm as the *logline* table (see :ref:`data-ext`). The discovered
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data is returned as a JSON-object that you can do further processing on.
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File Paths
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----------
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File path manipulation functions:
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* basename(s) - Return the file name part of a path.
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* dirname(s) - Return the directory part of a path.
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* joinpath(s1,s2,...) - Return the arguments joined together into a path.
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Networking
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----------
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Network information functions:
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* gethostbyname - Convert a host name into an IP address. The host name could
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not be resolved, the input value will be returned.
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* gethostbyaddr - Convert an IPv4/IPv6 address into a host name. If the
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reverse lookup fails, the input value will be returned.
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JSON
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----
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JSON functions:
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* jget(json, json_ptr) - Get the value from the JSON-encoded string in
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first argument that is referred to by the
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`JSON-Pointer <https://tools.ietf.org/html/rfc6901>`_ in the second.
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* json_group_object(key0, value0, ... keyN, valueN) - An aggregate function
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that creates a JSON-encoded object from the key value pairs given as
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arguments.
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* json_group_array(value0, ... valueN) - An aggregate function that creates
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a JSON-encoded array from the values given as arguments.
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Time
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----
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Time functions:
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* timeslice(t, s) - Given a time stamp (t) and a time slice (s), return a
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timestamp for the bucket of time that the timestamp falls in. For example,
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with the timestamp "2015-03-01 11:02:00' and slice '5min' the returned value
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will be '2015-03-01 11:00:00'. This function can be useful when trying to
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group together log messages into buckets.
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Internal State
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--------------
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The following functions can be used to access **lnav**'s internal state:
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* log_top_line() - Return the line number at the top of the log view.
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* log_top_datetime() - Return the timestamp of the line at the top of the log
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view.
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Collators
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---------
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* naturalcase - Compare strings "naturally" so that number values in the string
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are compared based on their numeric value and not their character values.
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For example, "foo10" would be considered greater than "foo2".
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* naturalnocase - The same as naturalcase, but case-insensitive.
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* ipaddress - Compare IPv4/IPv6 addresses.
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