logtime function exception safe

[elliVM]

Description

Logtime function throws exception in case functions fail, forcing the sql to run in throw none mode.

This change aims to allow the logtime epoch from path string extraction function to return 0 epoch instead of throwing an exception when used SQL functions fail.

• Extracts the logtime function into it's own object for easier unit testing
• Wrap in SQL COALESCE to provide 0 when getting NULL
• IFNULL check for SUBSTRING and use 1970010100 as fallback value

[kortemik]

making 1970 as a magick value is not really an option, better way would be to return a "sql null" in case extraction is not possible.

using

SELECT REGEXP_REPLACE(         '2010/01-08/sc-99-99-14-40/f17_v2/f17_v2.logGLOB-2010011601.log.gz','^\\d{4}\\/\\d{2}-\\d{2}\\/[\\w\\.-]+\\/([^\\p{Z}\\p{C}]+?)\\/([^\\p{Z}\\p{C}]+)(-@)?(\\d+|)-(\\d{4}\\d{2}\\d{2}\\d{2}).*',         '\\5' );
REGEXP_REPLACE(         '2010/01-08/sc-99-99-14-40/f17_v2/f17_v2.logGLOB-2010011601.log.gz','^\\d{4}\\/\\d{2}-\\d{2}\\/[\\w\\.-]+\\/([^\\p{Z}\\p{C}]+?)\\/([^\\p{Z}\\p{C}]+)(-@)?(\\d+|)-(\\d{4}\\d{2}\\d{2}\\d{2}).*',         '\\5' );

for example would provide better results. we should rather check that if extraction was successful and that it parses to date and then to unix date.

these can be verified with if(value regex 'valid value', unixtime(value), null) style