Interview Q&A / PostgreSQL
PostgreSQL interview questions
Indexes, EXPLAIN, transactions and isolation, JSONB and the Postgres specifics backend interviews probe.
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- What does the @> operator do on JSONB and why is it preferred for filtering?
a @> b is true when jsonb a contains jsonb b, meaning every key and value in b appears in a. It can use a GIN index, whereas filtering with ->> text comparisons usually cannot.
IntermediateQuick answer1 min read - What is a GIN index and which PostgreSQL features use it?
GIN is an inverted index: it maps each element (a word, an array item, a JSONB key) to the rows that contain it. It powers full-text search, array and JSONB containment queries, and trigram search, with slower writes than B-tree.
IntermediateQuick answer1 min read