Major Description
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.
POSSIBLE USES:
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