Section 2: Query Trees & Heuristic Optimization

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Last updated 7:21 PM on 9/25/26
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9 Terms

1
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Query Tree

Tree data structure representing relational algebra execution order[cite: 2]

2
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Leaf Nodes

Bottom nodes of a query tree representing input relations or tables[cite: 2]

3
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Internal Nodes

Tree nodes representing relational algebra operations (select, join, etc.)[cite: 2]

4
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Root Node

Topmost tree node whose execution outputs the final query result set[cite: 2]

5
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Execution Flow

Bottom-up evaluation starting from leaf nodes up to the root node[cite: 2]

6
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Predicate Pushdown

Heuristic rule moving selection (sigma) operations down close to base tables[cite: 2]

7
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Most Restrictive First

Heuristic rule executing selections that eliminate the most tuples first[cite: 2]

8
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Join Identification

Heuristic rule replacing Cartesian product (X) plus selection with equijoin[cite: 2]

9
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Projection Pushdown

Heuristic rule moving projection (pi) down to drop unused columns early[cite: 2]