Cost-based optimization in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main goal of cost-based optimization.

DBMS Theory

The primary goal of cost-based optimization is to minimize the [1] of executing a query.

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Atime

Bcost

Ccomplexity

Dsyntax

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing cost with time or complexity.

Thinking syntax errors are related to cost-based optimization.

Cost-based optimization aims to reduce the cost (resources used) to execute a query efficiently.

2fill in blank

medium

Complete the code to show what cost-based optimizers use to choose query plans.

DBMS Theory

Cost-based optimizers use [1] to estimate the expense of different query execution plans.

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Astatistics

Bheuristics

Csyntax rules

Dindexes

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing heuristics with statistics.

Thinking indexes are directly used for cost estimation.

Cost-based optimizers rely on statistics about data to estimate costs and choose the best plan.

3fill in blank

hard

Fix the error in the statement about cost-based optimization.

DBMS Theory

Cost-based optimization always chooses the query plan with the lowest [1] time.

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Acompile

Bnetwork

Cparsing

Dexecution

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking compile time is the main factor.

Confusing network or parsing time with execution time.

The optimizer aims to minimize execution time, not compile, network, or parsing time.

4fill in blank

hard

Fill both blanks to complete the cost estimation formula.

DBMS Theory

Total cost = [1] cost + [2] cost

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ACPU

BMemory

CI/O

DNetwork

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing memory or network cost as primary components.

Ignoring I/O cost which is often significant.

The total cost usually includes CPU cost and I/O cost, which are the main resource consumers.

5fill in blank

hard

Fill all three blanks to complete the description of cost-based optimization steps.

DBMS Theory

First, the optimizer collects [1]. Then it generates [2] plans. Finally, it selects the plan with the lowest [3].

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Astatistics

Bquery

Ccost

Dexecution

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing execution with cost in the final step.

Thinking the optimizer generates statistics as plans.

The optimizer collects statistics, generates query plans, and selects the plan with the lowest cost.