Column Granularity Indexing

BigQuery now offers column-granularity indexing, currently in public preview, to improve query performance and cost efficiency

BigQuery stores data in a columnar format, with each column having its own file block, enabling efficient data organization

The default search index maps data tokens to files, narrowing the search space by scanning only relevant files

File-level indexing struggles when search tokens are widespread across columns but selective within specific columns, leading to unnecessary file scans

Column-granularity indexing adds column-specific information to indexes, allowing BigQuery to pinpoint relevant data within specific columns

By identifying files with relevant tokens in specific columns, column-granularity indexing reduces the number of files scanned

Searching for "Google Cloud Logging" in the Title column scans only files containing all tokens in the Title column, improving efficiency

Column-granularity indexing significantly speeds up query execution times by accurately locating data within columns

Cost Savings: Reduced processed bytes and slot time lower query costs, making data analysis more cost-effective

Particularly beneficial for queries filtering or aggregating data based on specific columns or when tokens are common across files but selective within columns

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