Dynamic Fields in Apache Solr

So, you’ve installed a fresh copy of <a taget=”_blank” href=”http://lucene.apache.org/solr/”>Apache Solr</a>. You have tested it out running the examples from the <a href=”http://lucene.apache.org/solr/tutorial.html”>Solr tutorial</a>. And now you are ready to start indexing some of your own data. Just one problem. The fields for your own data are not recognized by your Solr instance. You notice in the schema.xml file that the default fields have names like cat, weight, subject, includes, author, title, payloads, popularity, price, etc. These fields are all defined for the purpose of being used with the sample data provided with Solr. Most of their names are likely not relevant to your search project, and even if you are willing to put up with misnamed fields at least for experimenting with your instance, you also face the problem that their set properties may not be what you would expect them to be.

Of course you can modify the schema.xml file and apply strong data-typing to each field that you plan to use to fit the exact needs of your project, reload Solr, and then start to index your data. But if you are just getting started with Solr, or starting a new project and experimenting with adding your dataset, you may not know exactly what fields you need to define or what properties to define for them. Or you might be interested updating an existing index with some additional fields, but do not want to add to explicitly add them to the schema.

Fortunately, Solr gives the option to define dynamic fields – fields that are defined in the schema with a glob-like pattern that is either at the beginning or end of the name. Further, there are pre-defined dynamic fields for most of the common data-types that you may use, in the default schema. Here are the some of the dynamic fields that are defined in the default schema.xml:

<dynamicField name="*_i"  type="int"    indexed="true"  stored="true"/>
<dynamicField name="*_s"  type="string"  indexed="true"  stored="true"/>
<dynamicField name="*_l"  type="long"   indexed="true"  stored="true"/>
<dynamicField name="*_t"  type="text"    indexed="true"  stored="true"/>
<dynamicField name="*_b"  type="boolean" indexed="true"  stored="true"/>
<dynamicField name="*_f"  type="float"  indexed="true"  stored="true"/>
<dynamicField name="*_d"  type="double" indexed="true"  stored="true"/>
<dynamicField name="*_dt" type="date"    indexed="true"  stored="true"/>

The field names are defined with a glob-like pattern that is either at the beginning or end of the name. With the above dynamic fields, you can index data with field names that begin with any valid string and end in one of the suffixes in the name attributes (i.e. article_title_s, article_content_t, posted_date_dt, etc.) and Solr will dynamically create any dynamic field of the particular type with the name that you give it. After you’ve indexed some data, you can actually view this dynamically created field in the schema viewer for your instance, located at http;//YOUR-INSTANCE/admin/schema.jsp

<field name="article_title_s">My Article</field>
<field name="article_content_t">Lorem Ipsum...</field>
<field name="posted_date_dt">1995-12-31T23:59:59Z</field>

How to Index a Site with Python Using solrpy and a Sitemap

If you are looking for a fast and easy way to populate a Solr instance using Python, read on.

The script provided here is a basic starting point to building the Solr index for any website with a sitemap, within minutes.  Simply modify the script to use your Solr instance and run with a path to your valid XML sitemap and it will begin populating your Solr index.

While you certainly can modify this script to fit your specific needs, you may even find that this script satisfies your Solr indexing requirements as-is.

To start, you need to be running Python 2.6 and have the following modules installed:

You can install these using easy_install or manually.

You will also require an Apache Solr instance.  (If you are looking for fully managed solution for hosting your Solr search application with a wide range of services, feel free to contact us.)

Ideally you will use this script on your own sitemap.  For detailed information on how to construct your sitemap click here: http://www.sitemaps.org/protocol.php.  You can search the web for other scripts that will automatically make sitemaps out of common CMS’s like WordPress and Joomla.  There are also sitemap generators available. You can also find a valid sitemap for testing here: http://www.google.com/sitemap.xml (~4Mb). We will assume that you have have a valid sitemap.

We will also assume that you have the default Solr schema.xml installed.

Write the following python script sitemap-indexer.py, replacing the value for solrUrl with the location of your own instance:

#! /usr/bin/env python26
""" Index links from a sitemap to a SOLR instance"""

import sys
from BeautifulSoup import BeautifulSoup
import solr
import hashlib
import urllib2
from xml.etree.ElementTree import parse

limit = 0 # How many iterations max?  Enter 0 for no limit.
solrUrl = 'http://localhost:8080/sitemap-indexer-test' # The URL of the solr instance
sitemaps_ns = 'http://www.sitemaps.org/schemas/sitemap/0.9' # The xmlns for the sitemap schema

if len(sys.argv) != 2:
	print 'Usage: ./sitemap-indexer.py path'

sitemapTree = parse(sys.argv[1])

solrInstance = solr.SolrConnection(solrUrl) # Solr Connection object

counter = 0
numAdded = 0

# Find all of the URLs in the form <url>...<loc>URL</loc>...</url>
for urlElem in sitemapTree.findall('{%s}url/{%s}loc'%(sitemaps_ns,sitemaps_ns)):
	counter = counter + 1 # Increment counter

	if limit > 0 and counter > limit:
		break; # For testing, you can set a limit to how many pages of the sitemap to consider

	url = urlElem.text # Get the url text from the element

		response = urllib2.urlopen(url) # Try to get the page at url
		print "Error: Cannot get content from URL: "+url
		continue # Cannot get HTML.  Skip.

		soup = BeautifulSoup(response.read()) # Try to parse the HTML of the page
		print "Error: Cannot parse HTML from URL: "+url
		continue # Cannot parse HTML.  Skip.

	if soup.html == None: # Check if there is an <html> tag
		print "Error: No HTML tag found at URL: "+url
		continue #No <html> tag.  Skip.

		title = soup.html.head.title.string.decode("utf-8") # Try to set the title
		print "Error: Could not parse title tag found at URL: "+url
		continue #Could not parse <title> tag.  Skip.

		body = str(soup.html.body).decode("utf-8") # Try to set the body
		print "Error: Could not parse body tag found at URL: "+url
		continue #Could not parse <body> tag.  Skip.

	# Note, decode("utf-8") is used to avoid non-ascii characters in the solrInstance.add below

	# Get an md5 hash of the url for the unique id
	url_md5 = hashlib.md5(url).hexdigest()

		# Add to the Solr instance
	except Exception as inst:
		print "Error adding URL: "+url
		print "\tWith Message: "+str(inst)
		print "Added Page \""+title+"\" with URL "+url
		numAdded = numAdded + 1

	solrInstance.commit() # Commit the additions
	print "Could not Commit Changes to SOLR Instance - Check SOLR logs for more info"
	print "Success. "+str(numAdded)+" documents added to index"

Make the script executable and run it:
./sitemap-indexer.py /path/to/sitemap.xml

It will start to go through the sitemap, parsing the content of each URL and if no errors found will add it to the Solr index. This process can take several minutes. There may be errors parsing many of the documents. They will simply be skipped, you may have to fine-tune the parser to fit your specific needs.

Once finished, it will output the number of documents that were committed to the Solr index.

You should be able to access your Solr Instance and run queries. There are numerous resources on the web to help you form query strings. There is also a query form in your Solr web admin interface that allows setting the various request parameters.

If you experience Solr Exceptions, check your Solr logs. If you modified your schema, be sure to reload your Solr instance as this may be the cause of Unrecognized Field Exceptions. You can find the default Solr schema in the example/solr/ directory of a new install of Solr.

If you would like to parse the documents for more specific tags than simply taking the entire body element (as this script does), refer to this documentation: