fix blocksel

[badboynt1]

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue #https://github.com/matrixorigin/MO-Cloud/issues/2946

What this PR does / why we need it:

fix blocksel

[matrix-meow]

@badboynt1 Thanks for your contributions!

Pull Request Review:

Problem 1: Lack of Detailed Description

The title and body of the pull request are quite vague. The title "fix blocksel" does not provide much context about the changes being made. The body of the pull request lacks a detailed explanation of why this fix is necessary and what specific issue it addresses. Providing more information in the title and body would help reviewers understand the purpose of the changes.

Suggestion 1: Improve Title and Description

• Title: Update the title to be more descriptive, such as "Enhance block selection logic in estimateFilterBlockSelectivity function."
• Body: Add a detailed description explaining the problem with the current block selection logic and how the changes in the pull request aim to address it. Mention any specific scenarios or bugs that were encountered.

Problem 2: Magic Numbers in Code

The changes in the code introduce magic numbers (e.g., 10, 0.7, 0.9) without clear explanations. Magic numbers can make the code harder to understand and maintain, as their purpose is not immediately clear to other developers.

Suggestion 2: Replace Magic Numbers with Constants or Comments

• Define constants for the magic numbers used in the code to give them meaningful names.
• Add comments next to the constants to explain their significance and why they were chosen.

Problem 3: Lack of Error Handling

The code changes do not include any error handling mechanisms. If there are potential errors that could occur during the execution of the estimateFilterBlockSelectivity function, they should be handled appropriately to prevent unexpected behavior or crashes.

Suggestion 3: Implement Error Handling

• Identify potential error scenarios in the function and add error handling mechanisms, such as returning errors or logging them for debugging purposes.
• Ensure that the function gracefully handles unexpected inputs or conditions to maintain the stability of the system.

Problem 4: Inconsistent Return Values

The return values in the estimateFilterBlockSelectivity function are inconsistent based on different conditions. This inconsistency can lead to confusion for developers trying to understand the logic flow of the function.

Suggestion 4: Ensure Consistent Return Values

• Review the logic in the function to ensure that the return values are consistent and follow a clear pattern based on the input conditions.
• Make sure that the return values are intuitive and align with the expected behavior of the function.

Security Concern: Potential Denial of Service (DoS) Vulnerability

The changes made in the pull request do not address any security concerns explicitly. However, the function estimateFilterBlockSelectivity appears to be related to query optimization, which is critical for performance. If the changes inadvertently introduce inefficiencies or vulnerabilities, they could potentially be exploited to launch a Denial of Service (DoS) attack by consuming excessive resources.

Suggestion 5: Perform Security Review

• Conduct a thorough security review of the changes to identify any potential vulnerabilities, especially related to performance and resource consumption.
• Implement safeguards or limits to prevent abuse or exploitation of the query optimization logic.

By addressing the issues mentioned above and considering the suggestions provided, the quality and maintainability of the codebase can be significantly improved. Additionally, incorporating security considerations into the review process will help ensure the overall robustness of the system.