What is the core mechanism of Solr1.3?

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Kernel calling mechanism

You can see from figure 3-3 that the Solr1.3 server contains a core API, also known as the kernel, that implements basic functions. All functions are implemented by calling the kernel API. The interface provided by API, the kernel of Solr1.3, has the characteristics of high cohesion and low coupling. Low coupling is mainly reflected in the fact that the functions including information query and index management can be realized only through an API function (execute). The format of the execute function call is shown in figure 3-3.

Figure 3-3 Solr kernel API call format

Although the same API calls are used for information queries and index management (including index add, update, and delete), the API parameters are different. For the query request SolrRequestHandler, the Handler,SolrQueryRequest responsible for information query is the information query parameter, and the SolrQueryResponse is the search result. For index management, SolrRequestHandler is the Handler,SolrQueryRequest responsible for index management, and SolrQueryResponse is the result of index management operation.

The low-coupling structure of kernel API makes it simple and clear logic structure, and the diversity of parameter subtypes of execute method makes this method have powerful function.

Sub-library mechanism

Sub-library mechanism (also known as multi-core mechanism) is a new mechanism introduced in Solr1.3, which has a strong demand in practical applications. For example, users do not want the index data of ordinary documents (Word, PDF, etc.) to be mixed with the index data of web pages, and want to choose whether to query ordinary documents or web pages, so it is necessary to index sub-database.

Solr1.3 sub-library can be achieved like this: under the home directory to establish a folder (or more, on behalf of the library), this folder called config and data folder, config folder to store custom schema.xml files and solrconfig.xml files, data folder to store index data; in the home directory under the solr.xml to add the above established library, the specific format see section 3.3.2.

Each library of Solr1.3 corresponds to each core of the server, each core is independent of each other, and each core can have independent document schema and system properties.

Caching mechanism

The response speed of search engine is an important measure of search engine performance. Because the index data is saved on the hard disk, as a peripheral device, the access speed of the hard disk is relatively slow; at the same time, because the querier obtains the corresponding query results from the index database, it will take a certain amount of time and resources to carry out some calculations; so there is a certain bottleneck in the speed of query. There may be duplicate queries in multiple users' queries, which provides an opportunity for us to cache some query results so that the next time users query again, they can quickly get the query results from the cache.

Solr provides a powerful caching mechanism to improve performance. Tables 3-15 list the various caches provided by Solr.

Table 3-15 caching in Solr

FilterCache

The unordered set of document ID, which can be queried accurately within a certain document.

QueryResultCache

The ordered table of the document ID, the result document of a query sorted according to a certain policy

DocumentCache

An object that stores the Document obtained from disk

User Caches

Custom cach

Solr also provides a cache "warm" mechanism, that is, how to get the data in the cache when the cache is established, one of which is to copy from the existing cache.

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