Dmitry Lychagin created ASTERIXDB-2272:
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Summary: Change character positions inside a string from 1-based
to 0-based
Key: ASTERIXDB-2272
URL: https://issues.apache.org/jira/browse/ASTERIXDB-2272
Project: Apache AsterixDB
Issue Type: Improvement
Components: FUN - Functions
Reporter: Dmitry Lychagin
Assignee: Dmitry Lychagin
Change how string functions count character positions inside a string.
Currently string functions position(), substring() and some others assume that
the first character is at position 1.
The proposal is to change the first position to 0, to better align with array
element positions (which also start with 0), and other languages.
This change will also apply to binary functions (below) and will be effective
in both SQLPP and AQL.
The following functions will be affected:
position(),
regexp_position(),
substring()/substr(),
sub_binary(),
find_binary()
This might be a disrupting change for some users so we will also introduce a
cluster-wide configuration parameter (“compiler.stringoffset”) for backwards
compatibility:
compiler.stringoffset = 0 // first character position is assumed to be 0 (new
default)
compiler.stringoffset = 1 // first character position is assumed to be 1
(backwards-compatible setting)
The query migration path is straightforward, for example:
substring(“abcdef”, 1) will need to be changed to substring(“abcdef”, 0), etc,
same applies to sub_binary().
position(), regexp_position(), and find_binary() will return one less than they
used to, but would still return -1 if the value is not found.
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