Skip to main content

Toolkit - Criteria for Dynamic Queries

This post if part of a series about the File System Toolkit - a custom content delivery API for SDL Tridion.

In the previous post Dynamic Content Queries, I presented a Query class that performs CustomMeta queries on JSON models published to the file system. This post presents the logic that actually queries for results and applies different boolean operators for different Criteria.

The base class for each criteria is Criterion, which defines the base methods each criteria must implement:

public abstract class Criterion {
    public Set<String> executeQuery() {
        return executeQuery(FilterImpl.EMPTY_FILTER);
    }

    public abstract Set<String> executeQuery(Filter filter);
}

The Filter class contains a set of allowed Publication ids, the item type and whether to include the range boundaries or not. The Filter is used in modifying the results retrieved for each criteria from the indexes.

Each criteria uses an index to lookup values associated to a given key. For example, a CustomMetaCriterion uses a key and value to retrieve all ComponentMeta or PageMeta that have a CustomMeta on that key with the specified value.

In order to do this lookup in a performant manner, there is an index where all keys and values are available (in ascending order) and by simply looking up an key-value tuple, we can retrieve the associated TcmUris of all items that have such key-value as CustomMeta. More information about these indexes is available in post Writing My Own Database Engine.

The CustomMetaCriterion uses the DateIndex, NumericIndex or StringIndex to lookup custom meta keys, depending on the type of the custom meta value (date, numeric or string).

In its simplest form, for a Key-StringValue CustomMeta, the executeQuery method builds an index key on the CustomMeta key and StringValue, then performs the StringIndex lookup for such key.

The result is a set of Strings representing the TcmUris that correspond to that index key in the StringIndex.

public Set<String> executeQuery(Filter filter) {
    String indexKey = stringIndex.buildKey(key, valueString);
    return new TreeSet<>(stringIndex.get(indexKey, filter));
}

The logical criteria (AndCriteria, OrCriteria) delegate their executeQuery to all sub-criteria and perform a logical intersection or union on the result sets. For example below, the AndCriteria below contains a list of sub-criteria that it needs to perform a logical AND between the result sets of each sub-criteria. As such, AndCriteria loops over the sub-criteria and then intersects their result sets:

public Set<String> executeQuery(Filter filter) {
    Set<String> result = null;
    boolean first = true;

    for (Criterion criterion : criteria) {
        Set<String> criterionResult = criterion.executeQuery(filter);

        if (first) {
            first = false;
            result = new TreeSet<>(criterionResult);
        } else {
            result.retainAll(criterionResult);
        }
    }

    return result;
}



Comments

Popular posts from this blog

Running sp_updatestats on AWS RDS database

Part of the maintenance tasks that I perform on a MSSQL Content Manager database is to run stored procedure sp_updatestats . exec sp_updatestats However, that is not supported on an AWS RDS instance. The error message below indicates that only the sa  account can perform this: Msg 15247 , Level 16 , State 1 , Procedure sp_updatestats, Line 15 [Batch Start Line 0 ] User does not have permission to perform this action. Instead there are several posts that suggest using UPDATE STATISTICS instead: https://dba.stackexchange.com/questions/145982/sp-updatestats-vs-update-statistics I stumbled upon the following post from 2008 (!!!), https://social.msdn.microsoft.com/Forums/sqlserver/en-US/186e3db0-fe37-4c31-b017-8e7c24d19697/spupdatestats-fails-to-run-with-permission-error-under-dbopriveleged-user , which describes a way to wrap the call to sp_updatestats and execute it under a different user: create procedure dbo.sp_updstats with execute as 'dbo' as

Content Delivery Monitoring in AWS with CloudWatch

This post describes a way of monitoring a Tridion 9 combined Deployer by sending the health checks into a custom metric in CloudWatch in AWS. The same approach can also be used for other Content Delivery services. Once the metric is available in CloudWatch, we can create alarms in case the service errors out or becomes unresponsive. The overall architecture is as follows: Content Delivery service sends heartbeat (or exposes HTTP endpoint) for monitoring Monitoring Agent checks heartbeat (or HTTP health check) regularly and stores health state AWS lambda function: runs regularly reads the health state from Monitoring Agent pushes custom metrics into CloudWatch I am running the Deployer ( installation docs ) and Monitoring Agent ( installation docs ) on a t2.medium EC2 instance running CentOS on which I also installed the Systems Manager Agent (SSM Agent) ( installation docs ). In my case I have a combined Deployer that I want to monitor. This consists of an Endpoint and a

Debugging a Tridion 2011 Event System

OK, so you wrote your Tridion Event System. Now it's time to debug it. I know this is a hypothetical situtation -- your code never needs any kind of debugging ;) but indulge me... Recently, Alvin Reyes ( @nivlong ) blogged about being difficult to know how exactly to debug a Tridion Event System. More exactly, the question was " What process do I attach to for debugging even system code? ". Unfortunately, there is no simple or generic answer for it. Different events are fired by different Tridion CM modules. These modules run as different programs (or services) or run inside other programs (e.g. IIS). This means that you will need to monitor (or debug) different processes, based on which events your code handles. So the usual suspects are: dllhost.exe (or dllhost3g.exe ) - running as the MTSUser is the SDL Tridion Content Manager COM+ application and it fires events on generic TOM objects (e.g. events based on Tridion.ContentManager.Extensibility.Events.CrudEven