Re: [xwiki-devs] [Proposal] Implement "distinct" in XWQL short queries through a QueryFilter

On Mon, Apr 16, 2012 at 9:59 PM, Vincent Massol&lt;vincent(a)massol.net&gt; wrote: > Hi, > > On Apr 16, 2012, at 8:10 PM, Jean-Vincent Drean wrote: > >> Hi devs, >> >> while replacing calls to xwiki#searchDocuments by calls to the query >> manager script service I ran into the following query manager issue: >> http://jira.xwiki.org/browse/XWIKI-7273 (XWQL short form queries >> should distinct on document fullname.) >> >> I think we could use the recent QueryFilter mechanism to handle the >> addition of the "distinct" in the select statement. >> https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwi… >> >> QueryFilters allow to: >> - transform queries depending on a dynamic parameter (for example the >> user preferences in HiddenDocumentFilter) >> - transform the select part of a short query, without requiring >> programming rights >> >> Here's an example of what it could look like from a velocity script: >> ----------------------------------------------------8<---------------------------------------------------- >> #set($query = $services.query.xwql("").addFilter("unique").addFilter("hidden")) >> ----------------------------------------------------8<---------------------------------------------------- >> Note that in the future we could decide that the Query wrapper we use >> in the QueryManagerScriptService (ScriptQuery) have the "unique" >> filter by default + a way to remove it from the script. >> >> I wasn't expecting us to consider using multiple filters when I added >> the new APIs in Query (4.0RC1). >> If we agree that a QueryFilter would be a nice way to handle this, I'd >> like to break those API before we release 4.0: >> ----------------------------------------------------8<---------------------------------------------------- >> - Query setFilter(QueryFilter filter); >> + Query addFilter(QueryFilter filter); >> - QueryFilter getFilter(); >> + List<QueryFilter> getFilters(); >> ----------------------------------------------------8<---------------------------------------------------- > > It's a little bit more complex. We did consider several filters when we added setFilter()!! :) > > We said that if we need more than one filter we could have an AndFilter() that takes a list of Filters. And allow more complex filters should we need them, like OrFilter, etc. > > #set($query = $services.query.xwql("").setFilter(new AndFilter("unique", "hidden")) > > Written with a fluent API that would give: > > #set($query = $services.query.xwql("").setFilter(and("unique", "hidden")) > > Or even: > > #set($query = $services.query.xwql("").setFilter("unique").and("hidden") > > Anyway I'm just mentioning this to explain what we thought about and an alternative to addFilter(). The only problem with addFilter() is if you need more complex Filters later on. It's not extensible whereas using AndFilter() and OrFilter() is more extensible at the expense of a little bit more text if not using a fluent api. Also you can't expose it that easily in velocity. For example your fluent APIs examples above won't work in velocity ; you would need a layer in between to adapt from script service APIs to the Java APIs.