Efficiently query an embedded database in a loop with prepared statements

问题

I asked a similar question the other day but have since realized I was getting ahead of myself. I'm seeking advice on the proper way to handle the following scenario. I'm trying to SELECT the correct longitude and latitude for a given address and city, in the fastest way possible.

My COORDINATES table has 25,000 rows and looks like this:

I have a Java HashMap<Integer, List<String>> which contains an Integer as the key, and an ArrayList containing 2 entries, an address and city. The HashMap has a size of 500.

There are 4 different types of SELECT statements I need to use, since each one is a little more lenient than the previous, like so:

SELECT LATITUDE, LONGITUDE FROM coordinates WHERE(address::text = ? AND community::text = ?) 
UNION ALL
SELECT LATITUDE, LONGITUDE FROM coordinates WHERE (address::text = ? AND community::text LIKE ?)
UNION ALL
SELECT LATITUDE, LONGITUDE FROM coordinates WHERE (address::text LIKE ? AND community::text = ?)
UNION ALL
SELECT LATITUDE, LONGITUDE FROM coordinates WHERE (address::text LIKE ? AND community::text LIKE ?)

Notice the use of LIKE and =. Also notice I'm using UNION ALL which aggregates all the results, whereas I'm actually only interested in the single, best matching result as to avoid continuing to query if a match is found. Perhaps a LIMIT could be helpful.

If I merely loop through my HashMap and hit the database 500+ times (with a 4-part query)... that seems painfully inefficent since I'm not leveraging the SQL server. It's taking over a minute right now. I'm using H2 as my embedded DB but am willing to use Derby or Hyper if needed.

• What is the fastest way to loop through the HashMap and retrieve the corresponding, best matching longitude/latitude (if any) for each entry? Notice I have to match up ? in the prepared statements with the corresponding address and city for each entry. Once again, you can view my current approach here.

• I'm leaning toward a stored procedure but the tutorials like this mention creating a JAR file of the stored procedure's class and then installing it to Derby. How do you deploy a standalone Java app that has an embedded DB relying on JAR stored procedure?

来源：https://stackoverflow.com/questions/45089887/efficiently-query-an-embedded-database-in-a-loop-with-prepared-statements