Most Efficient (Fast) T-SQL DELETE For Many Rows?

Question

Our server application receives information about rows to add to the database at a rate of 1000-2000 rows per second, all day long. There are two mutually-exclusive columns

Answer 1

Seems that your table is not indexed on (tag) and (longTag)

Build two indexes: one on (tag), one on (longTag)

If you are planning to delete a really big number of records, then declare two table variables, fill them with values and delete like this:

DECLARE @tag TABLE (id INT);
DECLARE @longTag TABLE (id VARCHAR(50));

INSERT
INTO  @tag
VALUES (`tag1`)

INSERT
INTO  @tag
VALUES (`tag2`)

/* ... */

INSERT INTO @longTag
VALUES ('LongTag1')

/* ... */


DELETE
FROM    MyRecords r
WHERE   r.tag IN (SELECT * FROM @tag)
        OR r.longTag IN (SELECT * FROM @longTag)

You may also try to perform a two-pass DELETE:

DELETE
FROM    MyRecords r
WHERE   r.tag IN (SELECT * FROM @tag)

DELETE
FROM    MyRecords r
WHERE   r.longTag IN (SELECT * FROM @longTag)

and see what statements runs longer, to see if there's an issue with the indexes.