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B-trees in PostgreSQL (cont)

Changes for PostgreSQL v12
  • indexes smaller
    • for composite keys, only store first attribute
    • index entries are smaller, so ci larger, so tree shallower
  • include TID in index key
    • duplicate index entries are stored in "table order"
    • makes scanning table files to collect results more efficient
To explore indexes in more detail:
  • \di+ IndexName
  • select * from bt_page_items(IndexName,BlockNo)