Quanlong Huang created IMPALA-11127:
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Summary: Document the UTF8_MODE query option and relavent string
functions
Key: IMPALA-11127
URL: https://issues.apache.org/jira/browse/IMPALA-11127
Project: IMPALA
Issue Type: Documentation
Affects Versions: Impala 4.1.0
Reporter: Quanlong Huang
Assignee: shajini thayasingh
Since IMPALA-2019 is resolved, we can document the UTF8_MODE query option added
in it now. The query option will turn on the UTF-8 aware behavior of string
functions. The relevant string functions and their UTF-8 aware behaviors are:
* LENGTH(STRING a)
** returns the number of UTF-8 characters instead of bytes
* SUBSTR(STRING a, INT start [, INT len])
SUBSTRING(STRING a, INT start [, INT len])()
** the substring start position and length is counted by UTF-8 characters
instead of bytes
* REVERSE(STRING a)
** the unit of the operation is a UTF-8 character, ie. it won't reverse bytes
inside a UTF-8 character.
* INSTR(STRING str, STRING substr[, BIGINT position[, BIGINT occurrence]])
LOCATE(STRING substr, STRING str[, INT pos])
** These functions have an optional position argument. The return values are
also positions in the string. In UTF-8 mode, these positions are counted by
UTF-8 characters instead of bytes.
* mask functions
** The unit of the operation is a UTF-8 character, ie. they won't mask the
string byte-to-byte.
* upper/lower/initcap
** These functions will recognize non-ascii characters and transform them
based on the current locale used by the Impala process.
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