How do efficiently display items on Google map in the viewing range of the user?

Question

When a user moves the Google map, I would like to display items in the viewing range of the user automatically. How can I efficiently and quickly display the items?

I have basic understanding of calling getBounds() method every time the user moves the map, but I am not sure how I can efficiently search and get from my database the items within the lat/lng of the bounds of the current viewport. Is there easier and faster way of doing this?

Answer 1

I've had the same issue. The way I tried to mitigate the problem is this.

• store the long/lat in the database as decimals
• put indexes on the long and lat columns
• use a query like SELECT * FROM table WHERE long > $long_left AND long < $long_right AND lat > $lat_bottom AND lat < $lat_top

I suggest you also use MarkerManager to handle the markers if you are expecting a large number of markers as you can set the markers to only display at certain zoom levels.

storing the long/lat as decimals lets the database compare the values correctly instead of having to convert the values before comparing them

indexes are key with databases (ha pun :-)) use them correctly but don't overuse them

Answer 2

In addition to Geek's answer, you may also want to consider creating an index on a Geohash instead. You could also use a database with spatial indexing capabilities. MySQL, PostgreSQL and SQL Server 2008 all have geo-spatial features (either natively or via extensions), which include spatial indexing.