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From "John Sichi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1518) context_ngrams() UDAF for estimating top-k contextual n-grams
Date Tue, 17 Aug 2010 22:30:16 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12899624#action_12899624

John Sichi commented on HIVE-1518:

Now there are a bunch of redundant casts remaining, e.g.

+      Double myval = (Double) ngrams.get(mykey);
+        Text word = (Text) other.get(i+j);

For cases like this, you can avoid the cast by keeping around the originally typed object:

+        ((ArrayList<Text>) curGram[0]).add(new Text(key.get(j)));

And for the Comparator, you can use Comparator<Map.Entry<ArrayList<String>,Double>>
to make it fully strongly typed and avoid casts.

> context_ngrams() UDAF for estimating top-k contextual n-grams
> -------------------------------------------------------------
>                 Key: HIVE-1518
>                 URL: https://issues.apache.org/jira/browse/HIVE-1518
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>    Affects Versions: 0.6.0
>            Reporter: Mayank Lahiri
>            Assignee: Mayank Lahiri
>             Fix For: 0.7.0
>         Attachments: HIVE-1518.1.patch, HIVE-1518.2.patch, HIVE-1518.3.patch
> Create a new context_ngrams() function that generalizes the ngrams() UDAF to allow the
user to specify context around n-grams. The analogy is "fill-in-the-blanks", and is best illustrated
with an example:
> SELECT context_ngrams(sentences(tweets), array("i", "love", null), 300) FROM twitter;
> will estimate the top-300 words that follow the phrase "i love" in a database of tweets.
The position of the null(s) specifies where to generate the n-gram from, and can be placed
anywhere. For example:
> SELECT context_ngrams(sentences(tweets), array("i", "love", null, "but", "hate", null),
300) FROM twitter;
> will estimate the top-300 word-pairs that fill in the blanks specified by null.
> 1. Pre-computing search lookaheads
> 2. Sentiment analysis for products or entities -- e.g., querying with context = array("twitter",
"is", null)
> 3. Navigation path analysis in URL databases

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