[CALCITE-6763] Optimize logic to select the tiles with the fewest rows

[xiaochen-zhou]

Our current logic using a PriorityQueue to select the tile with the fewest rows when multiple tiles are available. However, there are several potential issues:

1. The PriorityQueue stores all satisfiable tiles. When the number of tiles is large, maintaining the heap structure during element insertion has a time complexity of O(log n), which also increases memory usage.
2. The initial size of the PriorityQueue is difficult to estimate and is currently set to 1, causing frequent resizing of the PriorityQueue.

We can optimize the code by keeping only a single bestCandidate tile to improve performance.

[mihaibudiu]

There are no tests - is there any code calling this function?
If yes, then it's perhaps fine - the behavior is not supposed to change.

[xiaochen-zhou]

There are no tests - is there any code calling this function? If yes, then it's perhaps fine - the behavior is not supposed to change.

RelOptLattice#getAggregate() calling this function.

[mihaibudiu]

you can probably squash the commits

[xiaochen-zhou]

you can probably squash the commits

Done.

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[mihaibudiu]

There are some comments in Jira from @julianhyde, so I will wait to merge this.

[xiaochen-zhou]

There are some comments in Jira from @julianhyde, so I will wait to merge this.

OK.