I guess that it should be similar to how it is done in SQL for LIKE patterns.
You can introduce an escape character, e.g. ‘\’. Examples: ‘%’ - any string ‘\%’ - equal to ‘%’ character ‘\%foo%’ - starts from ‘%foo’ ‘%%%escape’ - ends with ’escape’ ‘\%%’ - starts from ‘%’ ‘\\\%%’ - starts from ‘\%’ . What do you think? Thanks, Mikhail > On 22 Sep 2016, at 16:47, DuyHai Doan <doanduy...@gmail.com> wrote: > > Hello Mikhail > > It's more complicated that it seems > > LIKE '%%escape' means EQUAL TO '%escape' > > LIKE '%escape' means ENDS WITH 'escape' > > What's about LIKE '%%%escape' ???? > > How should we treat this case ? Replace %% by % at the beginning of the > searched term ?? > > > > On Thu, Sep 22, 2016 at 3:31 PM, Mikhail Krupitskiy > <mikhail.krupits...@jetbrains.com <mailto:mikhail.krupits...@jetbrains.com>> > wrote: > Hi! > > We’ve talked about two items: > 1) ‘%’ as a wildcard in the middle of LIKE pattern. > 2) How to escape ‘%’ to be able to find strings with the ‘%’ char with help > of LIKE. > > Item #1was resolved as CASSANDRA-12573. > > Regarding to item #2: you said the following: >> A possible fix would be: >> >> 1) convert the bytebuffer into plain String (UTF8 or ASCII, depending on the >> column data type) >> 2) remove the escape character e.g. before parsing OR use some advanced >> regex to exclude the %% from parsing e.g >> >> Step 2) is dead easy but step 1) is harder because I don't know if >> converting the bytebuffer into String at this stage of the CQL parser is >> expensive or not (in term of computation) >> >> Let me try a patch > > So is there any update on this? > > Thanks, > Mikhail > > >> On 20 Sep 2016, at 18:38, Mikhail Krupitskiy >> <mikhail.krupits...@jetbrains.com <mailto:mikhail.krupits...@jetbrains.com>> >> wrote: >> >> Hi! >> >> Have you had a chance to try your patch or solve the issue in an other way? >> >> Thanks, >> Mikhail >>> On 15 Sep 2016, at 16:02, DuyHai Doan <doanduy...@gmail.com >>> <mailto:doanduy...@gmail.com>> wrote: >>> >>> Ok so I've found the source of the issue, it's pretty well hidden because >>> it is NOT in the SASI source code directly. >>> >>> Here is the method where C* determines what kind of LIKE expression you're >>> using (LIKE_PREFIX , LIKE CONTAINS or LIKE_MATCHES) >>> >>> https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/restrictions/SingleColumnRestriction.java#L733-L778 >>> >>> <https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/cql3/restrictions/SingleColumnRestriction.java#L733-L778> >>> >>> As you can see, it's pretty simple, maybe too simple. Indeed, they forget >>> to remove escape character BEFORE doing the matching so if your search is >>> LIKE '%%esc%', the detected expression is LIKE_CONTAINS. >>> >>> A possible fix would be: >>> >>> 1) convert the bytebuffer into plain String (UTF8 or ASCII, depending on >>> the column data type) >>> 2) remove the escape character e.g. before parsing OR use some advanced >>> regex to exclude the %% from parsing e.g >>> >>> Step 2) is dead easy but step 1) is harder because I don't know if >>> converting the bytebuffer into String at this stage of the CQL parser is >>> expensive or not (in term of computation) >>> >>> Let me try a patch >>> >>> >>> >>> On Wed, Sep 14, 2016 at 9:42 AM, DuyHai Doan <doanduy...@gmail.com >>> <mailto:doanduy...@gmail.com>> wrote: >>> Ok you're right, I get your point >>> >>> LIKE '%%esc%' --> startWith('%esc') >>> >>> LIKE 'escape%%' --> = 'escape%' >>> >>> What I strongly suspect is that in the source code of SASI, we parse the % >>> xxx % expression BEFORE applying escape. That will explain the observed >>> behavior. E.g: >>> >>> LIKE '%%esc%' parsed as %xxx% where xxx = %esc >>> >>> LIKE 'escape%%' parsed as xxx% where xxx =escape% >>> >>> Let me check in the source code and try to reproduce the issue >>> >>> >>> >>> On Tue, Sep 13, 2016 at 7:24 PM, Mikhail Krupitskiy >>> <mikhail.krupits...@jetbrains.com >>> <mailto:mikhail.krupits...@jetbrains.com>> wrote: >>> Looks like we have different understanding of what results are expected. >>> I based my understanding on >>> http://docs.datastax.com/en/cql/3.3/cql/cql_using/useSASIIndex.html >>> <http://docs.datastax.com/en/cql/3.3/cql/cql_using/useSASIIndex.html> >>> According to the doc ‘esc’ is a pattern for exact match and I guess that >>> there is no semantical difference between two LIKE patterns (both of >>> patterns should be treated as ‘exact match'): ‘%%esc’ and ‘esc’. >>> >>>> SELECT * FROM escape WHERE val LIKE '%%esc%'; --> Give all results >>>> containing '%esc' so %escapeme is a possible match and also escape%esc >>> Why ‘containing’? I expect that it should be ’starting’.. >>>> >>>> SELECT * FROM escape WHERE val LIKE 'escape%%' --> Give all results >>>> starting with 'escape%' so escape%me is a valid result and also escape%esc >>> Why ’starting’? I expect that it should be ‘exact matching’. >>> >>> Also I expect that “ LIKE ‘%s%sc%’ ” will return ‘escape%esc’ but it >>> returns nothing (CASSANDRA-12573). >>> >>> What I’m missing? >>> >>> Thanks, >>> Mikhail >>> >>>> On 13 Sep 2016, at 19:31, DuyHai Doan <doanduy...@gmail.com >>>> <mailto:doanduy...@gmail.com>> wrote: >>>> >>>> CREATE CUSTOM INDEX ON test.escape(val) USING >>>> 'org.apache.cassandra.index.sa >>>> <http://org.apache.cassandra.index.sa/>si.SASIIndex' WITH OPTIONS = >>>> {'mode': 'CONTAINS', 'analyzer_class': 'org.apache.cassandra.index.sa >>>> <http://org.apache.cassandra.index.sa/>si.analyzer.NonTokenizingAnalyzer', >>>> 'case_sensitive': 'false'}; >>>> >>>> I don't see any problem in the results you got >>>> >>>> SELECT * FROM escape WHERE val LIKE '%%esc%'; --> Give all results >>>> containing '%esc' so %escapeme is a possible match and also escape%esc >>> Why ‘containing’? I expect that it should be ’starting’.. >>>> >>>> SELECT * FROM escape WHERE val LIKE 'escape%%' --> Give all results >>>> starting with 'escape%' so escape%me is a valid result and also escape%esc >>> Why ’starting’? I expect that it should be ‘exact matching’. >>> >>>> >>>> On Tue, Sep 13, 2016 at 5:58 PM, Mikhail Krupitskiy >>>> <mikhail.krupits...@jetbrains.com >>>> <mailto:mikhail.krupits...@jetbrains.com>> wrote: >>>> Thanks for the reply. >>>> Could you please provide what index definition did you use? >>>> With the index from my script I get the following results: >>>> >>>> cqlsh:test> select * from escape; >>>> >>>> id | val >>>> ----+----------- >>>> 1 | %escapeme >>>> 2 | escape%me >>>> 3 | escape%esc >>>> >>>> Contains search >>>> >>>> cqlsh:test> SELECT * FROM escape WHERE val LIKE '%%esc%'; >>>> >>>> id | val >>>> ----+----------- >>>> 1 | %escapeme >>>> 3 | escape%esc >>>> (2 rows) >>>> >>>> >>>> Prefix search >>>> >>>> cqlsh:test> SELECT * FROM escape WHERE val LIKE 'escape%%'; >>>> >>>> id | val >>>> ----+----------- >>>> 2 | escape%me >>>> 3 | escape%esc >>>> >>>> Thanks, >>>> Mikhail >>>> >>>>> On 13 Sep 2016, at 18:16, DuyHai Doan <doanduy...@gmail.com >>>>> <mailto:doanduy...@gmail.com>> wrote: >>>>> >>>>> Use % to escape % >>>>> >>>>> cqlsh:test> select * from escape; >>>>> >>>>> id | val >>>>> ----+----------- >>>>> 1 | %escapeme >>>>> 2 | escape%me >>>>> >>>>> >>>>> Contains search >>>>> >>>>> cqlsh:test> SELECT * FROM escape WHERE val LIKE '%%esc%'; >>>>> >>>>> id | val >>>>> ----+----------- >>>>> 1 | %escapeme >>>>> >>>>> (1 rows) >>>>> >>>>> >>>>> Prefix search >>>>> >>>>> cqlsh:test> SELECT * FROM escape WHERE val LIKE 'escape%%'; >>>>> >>>>> id | val >>>>> ----+----------- >>>>> 2 | escape%me >>>>> >>>>> On Tue, Sep 13, 2016 at 5:06 PM, Mikhail Krupitskiy >>>>> <mikhail.krupits...@jetbrains.com >>>>> <mailto:mikhail.krupits...@jetbrains.com>> wrote: >>>>> Hi Cassandra guys, >>>>> >>>>> I use Cassandra 3.7 and wondering how to use ‘%’ as a simple char in a >>>>> search pattern. >>>>> Here is my test script: >>>>> >>>>> DROP keyspace if exists kmv; >>>>> CREATE keyspace if not exists kmv WITH REPLICATION = { 'class' : >>>>> 'SimpleStrategy', 'replication_factor':'1'} ; >>>>> USE kmv; >>>>> CREATE TABLE if not exists kmv (id int, c1 text, c2 text, PRIMARY KEY(id, >>>>> c1)); >>>>> CREATE CUSTOM INDEX ON kmv.kmv ( c2 ) USING >>>>> 'org.apache.cassandra.index.sa >>>>> <http://org.apache.cassandra.index.sa/>si.SASIIndex' WITH OPTIONS = { >>>>> 'analyzed' : 'true', >>>>> 'analyzer_class' : 'org.apache.cassandra.index.sa >>>>> <http://org.apache.cassandra.index.sa/>si.analyzer.NonTokenizingAnalyzer', >>>>> 'case_sensitive' : 'false', >>>>> 'mode' : 'CONTAINS' >>>>> }; >>>>> >>>>> INSERT into kmv (id, c1, c2) values (1, 'f22', 'qwe%asd'); >>>>> INSERT into kmv (id, c1, c2) values (2, 'f22', '%asd'); >>>>> INSERT into kmv (id, c1, c2) values (3, 'f22', 'asd%'); >>>>> INSERT into kmv (id, c1, c2) values (4, 'f22', 'asd%1'); >>>>> INSERT into kmv (id, c1, c2) values (5, 'f22', 'qweasd'); >>>>> >>>>> SELECT c2 from kmv.kmv where c2 like ‘_pattern_'; >>>>> >>>>> _pattern_ '%%%' finds all columns that contain %. >>>>> How to find columns that start form ‘%’ or ‘%a’? >>>>> How to find columns that end with ‘%’? >>>>> What about more complex patterns: '%qwe%a%sd%’? How to differentiate ‘%’ >>>>> char form % as a command symbol? (Also there is a related issue >>>>> CASSANDRA-12573). >>>>> >>>>> >>>>> Thanks, >>>>> Mikhail >>>>> >>>> >>>> >>> >>> >>> >> > >
