Events-csv Concepts: Difference between revisions

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* [[events-csv User Manual]]
* [[events-csv User Manual]]
=Tokenization=
The empty strings found between commas are interpreted as "[[#Missing_Value|missing value]]". For example:
a, , b
generates a data line with two values: <tt>"a"</tt> and <tt>"b"</tt>, separated by a [[#Missing_Value|missing value]].
The quoted empty strings found between commas are interpreted as empty strings. For example:
a,"  ", b
generates a data line with three values: <tt>"a"</tt>, <tt>"  "</tt> and <tt>"b"</tt>.
A line that ends in a comma generates a data line that has a [[#Missing_Value|missing value]] on the last position in line.
Then a comma-separated value line is turned into a CSVEvent, the [[#Missing_Value|missing values]] as defined above are represented with null-valued properties. If the type of the value is known, then the missing value is represented as a property of the corresponding type with a null value. For example:
# timestamp, count(int)
12/21/16 14:00:00,
will return a CSVEvent with a IntegerProperty "field_1". The value of the property will be null, which will carry [[#Missing_Value|missing value]] semantics.
On the other hand, when the header is missing, so we don't have a way of knowing the missing value's type, the missing value is represented with a null-valued UndefinedTypeProperty. In the following case:
a, , b
the corresponding CSVEvent carries a "field_1" UndefinedTypeProperty. which carries a null value.
=Missing Value=
=Headers=
The CSV parsers understand in-line header lines. A header line must start with # and must contain [[#CSV_Field_Specification|CSV field specifications]].
The headers can be extracted from a CSV stream with the [[Events-csv_User_Manual#headers|'headers' command]].
If a valid timed line ''immediately'' follows the header, the header will contain the timestamp for that line, expressed as [[Time#Millisecond_POSIX_Time|millisecond POSIX Time]], accessible as a "next-timed-event-timestamp" property. If a non-timed line follows, then the header event won't be expected to maintain a timestamp, even if subsequent lines are timed.


=CSV Format=
=CSV Format=
As mentioned above, [[#Headers|headers]] can be specified in-line. A header is prefixed with '#' and specifies the fields:
# timestamp(MM/dd/yy HH:mm:ss), collection-type(string), heap-occupancy(long)
Multiple headers are supported in the CSV line stream, and the parser adjust upon receiving a header, by parsing the data lines according to the latest header seen on the stream.
Comment lines are not allowed.


==CSV Field==
==CSV Field==


===CSV Field Specification===
===CSV Field Specification===
====Timestamp====


"timestamp", "timestamp(yy/MM/dd HH:mm:ss)", "timestamp(time:yy/MM/dd HH:mm:ss)"
"timestamp", "timestamp(yy/MM/dd HH:mm:ss)", "timestamp(time:yy/MM/dd HH:mm:ss)"


"something"
The timestamp can be specified as long representing [[Events-api_Concepts#Timestamp_Value|UTC milliseconds]], or as a string formatted using common date/time formats.


"something(string)"
If the UTC milliseconds is used, the CSV format/header should be specified as follows:
 
# timestamp(long), ...
 
====String Fields====
 
"something", "something(string)"
 
====Integer Fields====


"something(int)"
"something(int)"
====Long Fields====


"something(long)"
"something(long)"
====Float Fields====


"something(float)"
"something(float)"
====Double Fields====


"something(double)"
"something(double)"


"something(time)"
"something(time)"

Latest revision as of 19:45, 22 September 2017

Internal

Tokenization

The empty strings found between commas are interpreted as "missing value". For example:

a, , b

generates a data line with two values: "a" and "b", separated by a missing value.

The quoted empty strings found between commas are interpreted as empty strings. For example:

a,"   ", b 

generates a data line with three values: "a", " " and "b".

A line that ends in a comma generates a data line that has a missing value on the last position in line.

Then a comma-separated value line is turned into a CSVEvent, the missing values as defined above are represented with null-valued properties. If the type of the value is known, then the missing value is represented as a property of the corresponding type with a null value. For example:

# timestamp, count(int)
12/21/16 14:00:00, 

will return a CSVEvent with a IntegerProperty "field_1". The value of the property will be null, which will carry missing value semantics.

On the other hand, when the header is missing, so we don't have a way of knowing the missing value's type, the missing value is represented with a null-valued UndefinedTypeProperty. In the following case:

a, , b

the corresponding CSVEvent carries a "field_1" UndefinedTypeProperty. which carries a null value.

Missing Value

Headers

The CSV parsers understand in-line header lines. A header line must start with # and must contain CSV field specifications.

The headers can be extracted from a CSV stream with the 'headers' command.

If a valid timed line immediately follows the header, the header will contain the timestamp for that line, expressed as millisecond POSIX Time, accessible as a "next-timed-event-timestamp" property. If a non-timed line follows, then the header event won't be expected to maintain a timestamp, even if subsequent lines are timed.

CSV Format

As mentioned above, headers can be specified in-line. A header is prefixed with '#' and specifies the fields:

# timestamp(MM/dd/yy HH:mm:ss), collection-type(string), heap-occupancy(long)

Multiple headers are supported in the CSV line stream, and the parser adjust upon receiving a header, by parsing the data lines according to the latest header seen on the stream.

Comment lines are not allowed.

CSV Field

CSV Field Specification

Timestamp

"timestamp", "timestamp(yy/MM/dd HH:mm:ss)", "timestamp(time:yy/MM/dd HH:mm:ss)"

The timestamp can be specified as long representing UTC milliseconds, or as a string formatted using common date/time formats.

If the UTC milliseconds is used, the CSV format/header should be specified as follows:

# timestamp(long), ...

String Fields

"something", "something(string)"

Integer Fields

"something(int)"

Long Fields

"something(long)"

Float Fields

"something(float)"

Double Fields

"something(double)"

"something(time)"