Migrating to Terrier 5 from earlier versions

Command Line changes

Firstly, the bin/anyclass.sh and bin/trec_terrier.sh scripts are deprecated, and will be removed in a future release. You should aim to use bin/terrier from now on. For instance:

You can see all possible commands by typing bin/terrier help.

If you want to run an arbitrary class, you can still use bin/terrier com.org.MyClass. If you want your command to support commandline parsing, and appear in the bin/terrier help list, you should extend org.terrier.applications.CLITool.

Source code layouts

We have gone full Maven on the layout. The open source Terrier project has been broken down into Maven modules. See the documentation on Terrier's components for a list of the modules.

Each module is a separate dependency exported to MavenCentral. If you find that your project that depends on terrier-core no longer compiles, then you will need to select additional appropriate dependencies.

Index References and Remote Indices

Terrier 5 introduces IndexRef as a way to refer to an index. An IndexRef may not even be on the same machine - it may refer to an index served from an RESTful HTTP server. You can load a Manager (note Manager is now an interface rather than a concrete class) using ManagerFactory.from(indexRef)

How you interact with Terrier defines which Maven dependencies you need to load. If you only need to connect to a remote RESTful index, you need only depend on org.terrier:terrier-retrieval-api for compiling and org.terrier:terrier-rest-client at runtime. If you want a local index, then you will also need org.terrier:terrier-core at runtime.

There are minor changes to the API of the application-facing SearchRequest interface -- for more information, see the relevant Javadoc.

Index Formats

Terrier's index format has changed for Terrier 5. By default, Lexicons now retain the maximum tf observed in each term's posting list. This will allow future easier integration of dynamic pruning techniques such as WAND using a standard Terrier index.

Terrier 5 is backwardly compatible with Terrier 4 indices, i.e. Terrier 5 can use indices created by Terrier 4, without any need to re-index. Support for some earlier Terrier indices has not been retained (e.g. Terrier 3 block indices that use BlockLexiconEntry).

MatchingOp Query Language

Terrier now supports a subset of the Indri query language, called the matchop query language. See the new documentation about query language. You can use this query language by specifying -m to the interactive or batchretrieve Terrier commands. From your own code, you should set the terrierql:off and matchopql:on.

bin/terrier interactive -m 16:30:07.139 [main] INFO o.t.structures.CompressingMetaIndex - Structure meta reading lookup file into memory 16:30:07.146 [main] INFO o.t.structures.CompressingMetaIndex - Structure meta loading data file into memory 16:30:07.152 [main] INFO o.t.applications.InteractiveQuerying - time to intialise index : 0.086 Please enter your query: compressed chicken #combine(0.1 #uw1(compressed chicken)) 16:30:26.624 [main] INFO o.t.matching.PostingListManager - Query 1 with 3 terms has 3 posting lists

Using Extensions of Terrier

Terrier now supports loading in additional Maven dependencies. You can specify these using the terrier.mvn.coords property. For instance, if you have a number of your own custom Terrier weighting models installed in your local Maven repository, you could use these during retrieval by loading:

terrier.mvn.coords=com.org:myWmodels:5.0

This will search your local .m2 repository, as well as MavenCentral. The terrier.mvn.coords property takes a comma-delimited list of Maven dependencies, in the format of groupId:package:version. Snapshot versions are supported.