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Thread: Using UPPER and TRIM (INDEX usage)

Using UPPER and TRIM (INDEX usage)

From

Mintoo Lall

Date:

26 May 2003, 01:48:33

Hi Everybody,

How do I use "TRIM" and "UPPER" both in the SQL statement and still use the index.

I created an index on myTable in the following way

CREATE INDEX index_fname_myTable ON myTable USING btree (upper(fname));

Now the SQL I used was

SELECT * FROM myTable where upper(trim(fname))= 'JOHN':: character varying

The postgresql doesnt use the index on fname in the above case.

But if I use only "UPPER" in the SQL statement, the postgresql uses the index. For eg. SELECT * FROM myTable where upper(fname)= 'JOHN':: character varying

Any help is appreciated.

Regards

Mintoo

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Re: Using UPPER and TRIM (INDEX usage)

From

Christoph Haller

Date:

27 May 2003, 07:55:48

>> How do I use "TRIM" and "UPPER" both in the SQL statement and still 
use the index.>> I created an index on myTable in the following way>> CREATE INDEX index_fname_myTable ON myTable USING
btree(upper(fname));>> Now  the SQL I used was>>> SELECT * FROM myTable where upper(trim(fname))= 'JOHN':: character 
 
varying>> The postgresql doesnt use the index on fname in the above case.>> But if I use only "UPPER" in the SQL
statement,the postgresql uses 
 
the index.> For eg. SELECT * FROM myTable where upper(fname)= 'JOHN':: character 
varying

And what happens if you re-write it as

SELECT * FROM myTable where trim(upper(fname))= 'JOHN':: character varying

Alternatively try
CREATE FUNCTION uppertrim (character varying) returns character varying as '
select upper(trim($1));
' LANGUAGE SQL IMMUTABLE ;
and then
CREATE INDEX index_fname2_myTable ON myTable USING btree (uppertrim(fname));

Regards, Christoph