fix inappropriate heuristic method of estimating out-of-range values

[qw4990]

cherry pick for #18543

---

What problem does this PR solve?

Issue Number: close #18461

Problem Summary: If the estimated value is out of range, an inappropriate heuristic rule sel = 1/NDV*(modifyRows/totalRows) is used, which may cause unexpected low sel when a few rows are modified.

What is changed and how it works?

Change this rule to:

func outOfRangeEQSelectivity(ndv, modifyRows, totalRows int64) float64 {
	if modifyRows == 0 {
		return 0 // it must be 0 since the histogram contains the whole data
	}
	if ndv < outOfRangeBetweenRate {
		ndv = outOfRangeBetweenRate // avoid inaccurate selectivity caused by small NDV
	}
	selectivity := 1 / float64(ndv) // TODO: After extracting TopN from histograms, we can minus the TopN fraction here.
	if selectivity*float64(totalRows) > float64(modifyRows) {
		selectivity = float64(modifyRows) / float64(totalRows)
	}
	return selectivity
}

Check List

Tests

• Unit test

Release note

• planner: fix the inappropriate heuristic rule to estimate the EQ selectivity when out of range

[qw4990]

/run-all-tests

[winoros]

lgtm

[eurekaka]

LGTM

[eurekaka]

/merge

[ti-srebot]

/run-all-tests

[ti-srebot]

@qw4990 merge failed.

[qw4990]

/run-sqllogic-test-1