REFRESH NGRAM INDEX

Introduced or updated: v1.2.726

Databend automatically refreshes NGRAM indexes when data is ingested. Use REFRESH NGRAM INDEX when you need to backfill data that existed before the index was defined.

Syntax

REFRESH NGRAM INDEX [IF EXISTS] <index_name>
ON [<database>.]<table_name>;

Examples

-- Table already populated before the NGRAM index exists
CREATE TABLE IF NOT EXISTS amazon_reviews_ngram(review_id INT, review STRING);
INSERT INTO amazon_reviews_ngram VALUES
  (1, 'coffee beans from Colombia'),
  (2, 'best roasting kit');

-- Declare the NGRAM index afterward
CREATE NGRAM INDEX idx1 ON amazon_reviews_ngram(review) WITH (ngram_size = 3);

-- Refresh so the pre-existing rows are indexed
REFRESH NGRAM INDEX idx1 ON amazon_reviews_ngram;

-- Subsequent inserts refresh automatically in SYNC mode