How we can do full text search and facets stuffs on BigQuery?
Is BigQuery not suitable for above purpose? Do we need to stick with any RDBMS database (e.g., PostgreSQL, MySQL, etc.) and search engine (e.g., Solr, Elasticsearch, etc.) for this purpose?


Correct, BigQuery does not provide search or faceting capabilities. BigQuery is a data warehouse, so it's good for running analytics over large amounts of data, but it does not provide indexing, search, or facets.

You may be able to use Google Cloud Datastore (document database) for this, since it provides secondary indexes, or you may want to do as you suggested, and use a combination of a SQL database such as MySQL or PostgreSQL together with a search product such as Elasticsearch or Solr.