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Build HAWQ Vectorized Executor steps
-------------------------------------

1. Make sure HAWQ compilation and installation success.

2. execute "make ;make install" in vexecutor directory

3. add library name "vexector" to "shared_preload_libraries"
   in postgresql.conf which has to copies allocated in master 
   and segment data directories respectively. Make sure both 
   of them is assigned.
   
4. restart HAWQ cluster

5. execute "set vectorized_executor_enable to on" in psql 
   to activate vectorized execution


How to add the default vectorized data types and aggregate 
functions
----------------------------------------------------------

1. Follow "Build HAWQ Vectorized Executor steps" to start HAWQ.

2. execute "create_udv.sql" in psql. then some vectorized 
   data types and vectorized aggregate functions will be
   add to HAWQ.

3. If the default vectorized is no use, you can delete them by
   executing "clean_udv.sql" in psql.


How to add an new vectorized data types and operators
------------------------------------------------------

Vectorized data types is an new type like an array to storage a
series data, it must have a BASE types, For example, the base 
type of vint2 is int2. If you want to create an new vectorized 
data type, you can follow these steps:

1. Define the new struct and implement the IN/OUT functions 
   for the vectorized datatypes.
   
2. Create data types by SQL:
    a) Create an shell data types by CREATE TYPE;
    b) Register the IN/OUT functions to the PG_PROC by CREATE 
       FUNCTION;
    c) Create the actrual vectorized data types by CREATE TYPE,
       NOTE: Now we use typelem and typstorage of PG_TYPE to 
       mark the vectorized types.
       
3. Create the new operators for the new vectorized data types.

For example, If the base type is 'XXX', we want to create the 
vectorized data types for it:
    1) You can add the vectorized data types struct
       (e.g. Add to vtype.h)
            typedef struct vtype {
                int     _vl_len;
                Oid     elemtype;
                int     dim;
                bool    *isnull;
                bool    *skipref;
                Datum   values[0];
            }vtype;        

            typedef struct vtype vXXX;

       Implement the new IN/OUT functions for this data type:
     
            Datum vXXXin(PG_FUNCTION_ARGS);
            Datum vXXXout(PG_FUNCTION_ARGS);
       
    2) Create data types by SQL:
    
            CREATE TYPE vXXX;
            CREATE FUNCTION vXXXin(cstring)......;
            CREATE FUNCTION vXXXout(vXXX)......;
            CREATE TYPE vXXX ( INPUT = vXXXin, 
                               OUTPUT = vXXXout, 
                               element = XXX, 
                               storage=external );
        
    3) Add new operators for the vectorized data types:
    
        CREATE FUNCTION vXXXvXXXgt(vXXX, vXXX) ......;
        CREATE OPERATOR > ( leftarg = vXXX, 
                            rightarg = vXXX, 
                            procedure = vXXXvXXXgt, 
                            commutator = <= );