Making custom full text search on mysql (making index file)

If you are only going to implement what MySQL calls boolean mode (no relevance counting), you should implement the following basic functionality:

1. A wordbreaker, an algorithm that splits the strings into words. This is trivial in English but can be a problem for some Asian languages which do not use spaces between words.

2. Optionally, a stemmer, an algorithm which reduces words to their basic forms, so that went and gone both become go.

3. Optionally, a spellchecker, an algorithm which corrects the common spelling errors.

4. Optionally, a thesaurus, which reduces the synonyms to their common form.

A result of all this is that you have a string like this:

a fast oburn vixen jmups over an indolent canine

split into the basic forms of the words with the synonyms replaced and errors corrected:

quick
brown
fox
jump
over
lazy
dog

Then you just create a composite index on (word, rowid), where word is the basic form and rowid is the PRIMARY KEY of the record indexed.

To query for, say, '+quick +fox', you should search your index for these words and find an intersection on rowid. The intersecting rowid will contain both words.

If you are going to take relevance into account, you should additionally maintain a per-word statistics in a separate index over the whole corpus.

I should warn you that this is not a simple task. Just take a look at Sphinx source code.

Don't do it
Unless you know what you are doing forget about rolling your own full-text-search.
Let MySQL do the heavy lifting.

1. Use MyISAM for the table your want to search on
2. Put a FULLTEXT index on the text-fields you want to index.

Then do

SELECT *, MATCH(field1, field2) AGAINST 'text to search' 
  IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION AS relevancy 
FROM table1 
WHERE MATCH(field1, field2) AGAINST 'text to search' 
  IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION
ORDER BY relevancy

See: http://dev.mysql.com/doc/refman/5.5/en/fulltext-search.html#function_match

OP indicated that he want to search for word endings.

Where I live (Holland) we do poems in December, so I do a lot of word ending searching to find words that ryhme.
Here's my trick.

Add a new field to your table named visa_versa: varchar indexed

UPDATE mytable SET mytable.visa_versa = REVERSE(mytable.myword);

Now you can do an indexed search on word endings with

SET @ending = 'end';
SELECT myword FROM mytable where visa_versa LIKE REVERSE(CONCAT('%',@ending));