Advanced Filter Caching in Solr

10 02 2012


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MurmurHash3 for Java

15 09 2011

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Solr’s Realtime Get

7 09 2011

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Solr relevancy function queries

10 03 2011

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Solr Result Grouping / Field Collapsing Improvements

17 12 2010

I previously introduced Solr’s Result Grouping, also called Field Collapsing, that limits the number of documents shown for each “group”, normally defined as the unique values in a field or function query.

Since then, there have been a number of bug fixes, performance improvements, and feature enhancements. You’ll need a recent nightly build of Solr 4.0-dev, or the newly released LucidWorks Enterprise v1.6, our commercial version of Solr.

Feature Enhancements

One improvement is the ability to group by query via the group.query parameter. This functionality is very similar to facet.query, except that it retrieves the top documents that match the query, not just the count. This has many potential uses, including always getting the top documents for specific groups, or defining custom groups such has price ranges.

Another useful capability is the addition of the group.main parameter. Setting this to true causes the results of the first grouping command to be used as the main result list in a flattened response format that legacy clients will be able to handle.

For example, the grouped response format normally returns highly structured results under “grouped”.

     "groupValue":"Apache Software Foundation",
        "name":"Solr, the Enterprise Search Server",
        "manu":"Apache Software Foundation"}]
     "groupValue":"Corsair Microsystems Inc.",
        "name":"CORSAIR ValueSelect 1GB 184-Pin DDR SDRAM Unbuffered DDR 400 (PC 3200) System Memory - Retail",
        "manu":"Corsair Microsystems Inc."}]

If we add group.main=true to the request, then we get back a much more familiar looking response (i.e. it looks like a normal non-grouped response):

    "name":"Solr, the Enterprise Search Server",
    "manu":"Apache Software Foundation"},
    "name":"CORSAIR ValueSelect 1GB 184-Pin DDR SDRAM Unbuffered DDR 400 (PC 3200) System Memory - Retail",
    "manu":"Corsair Microsystems Inc."},

One can also use the group.format=simple parameter to select this simplified flattened response within the normal “grouped” section of the response.

Other recent enhancements include support for debugging explain, highlighting, faceting, and the ability to handle missing values in the grouping field by treating all documents without a value as being in the “null” group.

Performance Enhancements

There have been a number of performance enhancements, including an improvement to the short circuiting logic… cutting off low ranking documents earlier in the process. This important optimization resulted in a speedup of about 9x for collapsing on certain fields!

Collapsing on string fields was further optimized with specialized code that worked on ord values instead of the string values. This doubled the performance yet again!

Please see the Solr Wiki for further documentation on all of result grouping’s capabilities and parameters.

Indexing JSON in Solr 3.1

8 12 2010

Solr has been able to produce JSON results for a long time, by adding wt=json to any query. A new capability has recently been added to allow indexing in JSON, as well as issuing other update commands such as deletes and commits.

All of the functionality that was available through XML update commands can now be given in JSON.
For example, you can index a document like so:

$ curl http://localhost:8983/solr/update/json -H 'Content-type:application/json' -d '
  "add": {
    "doc": {
      "id" : "ISBN:978-0641723445",
      "title" : "The Lightning Thief",
      "author" : "Rick Riordan",
      "series_t" : "Percy Jackson and the Olympians",
      "cat" : ["book","hardcover"],
      "genre_s" : "fantasy",
      "pages_i" : 384,
      "price" : 12.50,
      "inStock" : true,
      "popularity" : 10

Of course, if you want the doc to be visible, you must do a commit. This could have been done by adding a commit=true parameter to the URL in the previous command, or we could have added a commit command within the JSON itself. This time we’ll issue a separate commit command.

curl "http://localhost:8983/solr/update/json?commit=true"

And now, we can query the Solr index and verify the document has been correctly added (requesting the results in JSON of course!)


There’s more documentation on the Solr Wiki.
To use this functionality, you’ll need to use LucidWorks Enterprise (our commercial version of Solr), or a recent Solr 3.1-dev or 4.0-dev nightly build.

Solr Result Grouping / Field Collapsing

16 09 2010

Result Grouping, also called Field Collapsing, has been committed to Solr!
This functionality limits the number of documents for each “group”, usually defined by the unique values in a field (just like field faceting).

You can think of it like faceted search, except instead of just getting a count, you get the top documents for that constraint or category. There are tons of potential use cases:

  • For web search, only show 1 or 2 results for a given website by collapsing on a site field.
  • For email search, only show 1 or 2 results for a given email thread
  • For e-commerce, show the top 3 products for each store category (i.e. “electronics”, “housewares”)
  • Hiding duplicate documents at query time.

In addition to being able to group by the values of a field, you can also group by the values of a function query. Given that geo search works as a function query, this also opens up possibilities for showing top query matches within 1 mile, between 1 and 2 miles, etc.

Just like faceting, we’ll be adding new functionality and making continual improvements.
Result Grouping is documented on the Solr Wiki, and you will need a recent
nightly build of Solr 4.0-dev to try it out (just make sure it’s dated after this post).