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From zellerh <...@git.apache.org>
Subject [GitHub] incubator-trafodion pull request: [TRAFODION-762] support HIVE dat...
Date Thu, 26 May 2016 00:53:31 GMT
Github user zellerh commented on a diff in the pull request:

    https://github.com/apache/incubator-trafodion/pull/496#discussion_r64677400
  
    --- Diff: core/sql/optimizer/NATable.cpp ---
    @@ -3553,6 +3553,48 @@ NAType* getSQColTypeForHive(const char* hiveType, NAMemory* heap)
       if ( !strcmp(hiveType, "timestamp"))
         return new (heap) SQLTimestamp(TRUE /* allow NULL */ , 6, heap);
     
    +  if ( !strcmp(hiveType, "date"))
    +    return new (heap) SQLDate(TRUE /* allow NULL */ , heap);
    +
    +  if ( !strncmp(hiveType, "varchar", 7) )
    +  {
    +    char maxLen[32];
    +    memset(maxLen, 0, 32);
    +    int i=0,j=0;
    +    int copyit = 0;
    +
    +    //get length
    +    for(i = 0; i < strlen(hiveType) ; i++)
    +    {
    +      if(hiveType[i] == '(') //start
    +      {
    +        copyit=1;
    +        continue;
    +      }
    +      else if(hiveType[i] == ')') //stop
    +        break; 
    +      if(copyit > 0)
    +      {
    +        maxLen[j] = hiveType[i];
    +        j++;
    +      }
    +    }
    +    Int32 len = atoi(maxLen);
    +
    +    if(len == 0) return NULL;  //cannot parse correctly
    +
    +    NAString hiveCharset =
    +        ActiveSchemaDB()->getDefaults().getValue(HIVE_DEFAULT_CHARSET);
    +
    +    return new (heap) SQLVarChar(CharLenInfo((hiveCharset == CharInfo::UTF8 ? 0 : len),len),
    --- End diff --
    
    One solution is to do this mapping:
    
    Hive STRING ==> Trafodion VARCHAR(n BYTES), with n determined by HIVE_MAX_STRING_LENGTH
    
    Hive VARCHAR(n) ==> Trafodion VARCHAR(n)
    
    This treats STRING and VARCHAR differently, the max size of STRING is in bytes, the max
size of VARCHAR is in characters. This is not ideal, users will probably expect string + CQD
HIVE_MAX_STRING_LENGTH 'n' to work similar to VARCHAR(n)?
    
    There is no good way to achieve this, though, at least not without wasting space and making
incompatible changes.
    
    I wonder what other people think.


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