Businesses using Google's hosted site search service will now have the ability to trigger a re-indexing of their site whenever they want.

Google's decision to enhance its hosted site search service for businesses means that web publishers now have control over the frequency with which Google refreshes its index of the site's content, something that until now had been automatically scheduled by Google's system based on internal algorithms.

Site Search's On-Demand Indexing will go live on Thursday. In their Site Search control panel, web publishers will see a new button labelled "index now" that, when clicked on, will activate this new feature.

"On demand indexing is like supercharging the Site Search product so that our customers - the website owners - can come to Google as their websites are changing and say 'I just added 100 or 1,000 pages - please index them now,'" said Nitin Mangtani, Google's lead product manager for enterprise search.

On-Demand Indexing should come in handy when a site has been redesigned and is being relaunched or when a lot of content has been added to it or changed, he said.

The newly-indexed pages should become searchable no later than 24 hours after the re-indexing is requested.

"We're giving new pages a fast-pass so they can be quickly indexed and get through our indexing pipeline right away," he said.

Site Search, a web-hosted service that doesn't require any software installation by customers, is designed for companies that want to use Google technology to power the search engine on their sites.

Previously called Google Custom Search Business Edition, Site Search got its current name in June, along with a set of significant upgrades, including a more comprehensive indexing capability and more granular options for ranking search results.

Site Search starts at an annual $100 (£67) for websites of up to 5,000 pages and includes up to 250,000 search queries per year. A $500 (£335) second tier exists for sites with 5,001 to 50,000 pages and also limits queries to 250,000 per year.

The price goes up to $850 per year for sites with between 50,001 and 100,000 pages, but the annual query ceiling rises to 500,000. For sites with 100,001 to 300,000 pages the price is $2,250 per year with a 500,000 annual query maximum.

Web publishers with larger sites need to contact Google for pricing. Currently, thousands of businesses use Site Search, including Adobe and Con Edison, according to Mangtani.

A less sophisticated web hosted site search service called Custom Search Engine AdSense for Search is free and requires web publishers to carry Google ads.

Google also sells the Mini and Search Appliance computers, which use Google search engine software to index both a company's publicly available Web pages as well as internal files and documents with access restrictions.