use selfJoinCard for expectedRightRows estimate

angelamayxie · angelamayxie · commit 7a77707c2013 · 2025-07-16T16:33:48.000-07:00
diff --git a/sql/memo/coster.go b/sql/memo/coster.go
@@ -132,9 +132,9 @@ func (c *coster) costRel(ctx *sql.Context, n RelExpr, s sql.StatsProvider) (floa
 				}
 
 				// The total expected number of right row lookups
-				expectedRightRows := lBest * matchRate
+				expectedRightRows := selfJoinCard * matchRate
 				// Estimate for reading each left row and each expected right row
-				return lBest*seqIOCostFactor + expectedRightRows*randIOCostFactor, nil
+				return lBest*seqIOCostFactor + expectedRightRows*(randIOCostFactor+seqIOCostFactor), nil
 			case *ConcatJoin:
 				return c.costConcatJoin(ctx, n, s)
 			}

Original file line number	Diff line number	Diff line change
`@@ -132,9 +132,9 @@ func (c coster) costRel(ctx sql.Context, n RelExpr, s sql.StatsProvider) (floa`
`132`	`132`	`}`
`133`	`133`
`134`	`134`	`// The total expected number of right row lookups`
`135`		`- expectedRightRows := lBest * matchRate`
	`135`	`+ expectedRightRows := selfJoinCard * matchRate`
`136`	`136`	`// Estimate for reading each left row and each expected right row`
`137`		`- return lBestseqIOCostFactor + expectedRightRowsrandIOCostFactor, nil`
	`137`	`+ return lBestseqIOCostFactor + expectedRightRows(randIOCostFactor+seqIOCostFactor), nil`
`138`	`138`	`case *ConcatJoin:`
`139`	`139`	`return c.costConcatJoin(ctx, n, s)`
`140`	`140`	`}`