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Chapter 6 · Watch, then practise

File Structure & Hashing

Choose storage access paths from the operations a workload needs, especially equality lookup, ordered retrieval and range scans.

3 questions · 3 with related videos. Matches are based on playlist titles; broader background matches are labeled.

What to study

  • File organization and access paths
  • B-tree indexes
  • Hash indexes
  • Range and equality queries

Chapter playlists

Existing playlist: File Structure & Hashing

Notes

Introduction To B+ tree Explained in Hindi l DBMS Course

5 Minutes Engineering · 8:34

Choose a video · 2 lectures

B+ tree and hashing lectures provide the access-path comparison behind a range query.

1. Tree versus hash

Which index is a natural fit for marks BETWEEN 50 AND 70?

A B-tree preserves an ordering and supports range comparisons as well as equality. A hash index is designed around equality of hashed keys and does not provide useful key order for a range scan. Choose by query pattern, not by assuming hashing is always faster.

Introduction To B+ tree Explained in Hindi l DBMS Course

5 Minutes Engineering · 8:34 · Background lecture

B+ tree ordering is useful background for ordered retrieval. The playlist title does not establish coverage of PostgreSQL ORDER BY planning.

2. Ordered retrieval

Can an index help an ORDER BY query?

An appropriate B-tree can return keys in sorted order, sometimes avoiding a separate sort. That is not always the cheapest plan: when many rows are needed, a scan followed by sorting may still win. The optimizer estimates these alternatives.

L-6.1: What is hashing with example | Hashing in data structure

Gate Smashers · 5:53

Choose a video · 2 lectures

Hashing and B+ trees are the two relevant access methods; apply their properties to equality and date-range predicates.

3. Access-path decision

A table is searched by exact ID and by date range. Is one hash index enough?

No. It can support exact equality on the indexed ID but does not supply date ordering. A B-tree on date supports date-range predicates. These indexes are separate access structures; they do not replace the table or automatically improve every query.

References