[TIP] Partial Index in Valentina Database.

Today one of user have asked if Valentina supports partial index. Answer is YES OF COURSE, you can easy create a partial index using Table Methods.

Partial index of a Table field means that index stores values of column partially. You can reduce data
* horisontally – use e.g. only first N chars of a VarChar field
* vertically – use values of not all records.

Example 1 – Partial Horizontally

Let’s create VarChar Table Method, which takes only first 5 chars of URL.
We make this method to be indexed.

fldURL_5 = tbl.CreateVarChar( “fldURL_5”, 2044, fIndexed, “left(fldURL, 5)” )

Now you can do effective search as:  … WHERE fldURL_5 LIKE ‘A%’
Really, if average length of URL is 100 chars, then index becomes at least 20 times less.
Speed therefore is increased also.

Example 2 – Partial Vertically