Or: how to compare chars from different languages? How to compare Cyrillic "T" to latin "T"? In UTF/Unicode such comparison is possible (and Vertica data encoded in UTF-8). FYI: For UTF/Unicode its a big problem/challenge - case sensitive comparison, because same letters in different languages can has different order. I don't know what strategy Vertica choose, both strategies has same complexity in worst case => O(length of string). Can be another strategy: convert all strings to same case (lower or upper) and prepare case-sensitive comparison. test=> select ascii('a'), ascii('A'), 'a' > 'A' ascii | ascii | ?column? -+-+- 97 | 65 | t (1 row) So non-case sensitive search require 2 comparison for decision: character compared to "small" AND "capital" letter. Here I want to point out that I like to read books written by real developers, database administrators, people with practical experience, not theorists. For example ASCII table comparison: small "a" = 97, while capital "A" = 65. This example creates a table containing several strings to demonstrate regular expressions.Hi! Case-sensitive search ALWAYS will be faster than non sensitive, because it compares chars by their order in characters table. If you are porting a regular expression query from an Oracle database, remember that Oracle considers a zero-length string to be equivalent to NULL, while Vertica does not. If string exists in a raw column of a flex or columnar table, cast. To see all the queries currently running: vsql> select username, sessionid, transactionid, statementid, request, requestdurationms, starttimestamp from queryrequests where isexecuting't' order by starttimestamp desc 'queryrequests' is a system view built over few system tables, but this is only available in Vertica 6.0 and above. This function operates on UTF-8 strings using the default locale, even if the locale has been set to something else. The VARCHAR or LONG VARCHAR string to search for a regular expression pattern match. All spaces in the regular expression that you want to be matched in strings must be escaped with a backslash ( \) character. Comments start with a hash ( #) character and end with a newline ( \n). Using the x modifier causes the function to ignore all unescaped space characters and comments in the regular expression.
from your iOS device to a Mac computer and iTunes, browse your iTunes and iCloud backups of your iPhone like a normal USB flash drive. It offers a new approach to system maintenance that will: transfer files like apps, photos, music, contacts etc. Can execute it via column-oriented DBMS like Clickhouse and Vertica, transfering systems like Apache Kafka and. operator matches any character except a newline.Īdd comments to your regular expressions. iLike is an all-in-one utility geared towards accessing your iPhone, iPad and iPod touch. Without the m modifier, the start and end of line operators match only the start and end of the string.Īllow the single character regular expression operator (. Using this modifier, the start of line ( ^) and end of line ( $) regular expression operators match line breaks ( \n) within the string. Treat the string to match as multiple lines. Treat strings as binary octets, rather than UTF-8 characters.įorce the match to be case sensitive (the default). One or more single-character flags that modify how the regular expression finds matches in string: b See the Perl Regular Expressions Documentation for details. The syntax of the regular expression is compatible with the Perl 5 regular expression syntax.
If string exists in a _raw_ column of a flex or columnar table, cast string to a LONG VARCHAR before searching for pattern.Ī string containing the regular expression to match against the string. The VARCHAR or LONG VARCHAR string to search for a regular expression pattern match. Syntax REGEXP_LIKE( string, pattern ) Parameters string LIKE, ILIKE, and RLIKE all perform similar operations however, RLIKE uses POSIX EXE (Extended Regular Expression) syntax instead of the SQL pattern syntax used by LIKE and ILIKE. Unlike the LIKE function, string matching is case-insensitive. This function is similar to the LIKE-predicate, except that it uses regular expressions rather than simple wildcard character matching. Allows matching of strings based on comparison with a pattern. Returns true if the string matches the regular expression.