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README for plsql-hashtable

ABOUT:

When you are developing oracle object one very useful datatype is not available, that is assosiative arrays. Assosiative arrays is hashtables for oracle-plsql, but can only be used within plsql structures. Another limitation of assosiative arrays is that the index key should be either varchar2(30) or pls_integer. 
Do you find yourself programming only within plsql-packages, never with Object types, and is the structure never to be stored on the database, then stick to assositive arrays - it's native plsql and it's very fast.

Do you, on the other hand:
 1. need a hashtable in an Object type
 2. need a different index than varchar2 or pls_integer
 3. need to store the collection into the database
 4. need hashtables with multiple key types and value types
Then by all means, use this code.


INSTALLATION NOTES:

Run either the install.sql or alt-install.sql file on your database schema. 
WARNING: Any object, package, procedure, function or table with the following names will be dropped: 
         HASHTABLE, HASH_BUCKET_ARRAY, HASH_BUCKET, HASH_ENTRY


API DESCRIPTION:

The object "hashtable" is initialized through the "hashtable()" constructor.

The interaction is done with these five methods:
  put(key anydata, value anydata)
  get(key anydata) return anydata
  remove(key anydata)
  exist(key anydata) return boolean
  count return number

To use a type in the hashtable, the methods "hash(key anydata)" and "equals(key1 anydata, key2 anydata)" must be modified to handle the key type. Overloaded methods to store varchar2 and number as key-value pairs has been implemented as an example. The implementation is located at the end of the hashtable body. 


USAGE: See the file "test.sql".


SPECIALIZED EXAMPLE:

Conversion to anydata and extra method call's are computational expensive. A specialized version of the hashtable is much faster. The only changes that you would need to make are in the HASH_ENTRY type and the method variable types in the HASHTABLE type. Read alt-hashtable.typ to see how.


CHANGE LOG:

0.2 Changes:
add    : Install script
add    : Test SQL of insert
add    : Added alternative specialized hashtable as an example. Is doing fewer conversions and is faster.
rewrite: Realized that buckets was linked lists - changed type to VARRAY(100).
         Result - faster structure (should be constant access), but array doubling doesn't work anymore.
         Bucket reorder no longer needed as VARRAY retain the order of elements.
bug fix: Array not properly initialised when doing array doubling.
         Obsolete when VARRAY was introduced.
problem: Arrays doubling is not possible when using VARRAY.


0.1 Initial release:
Content: one single sql file with four types.