Commitbf09437

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Fix GiST README's explanation of the NSN cross-check.

The text got the condition backwards, it's "NSN > LSN", not "NSN < LSN".While we're at it, expand it a little for clarity.Reviewed-by: Daniel GustafssonDiscussion:https://www.postgresql.org/message-id/4cb46e18-e688-524a-0f73-b1f03ed5d6ee@iki.fi

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Original file line number	Diff line number	Diff line change
`@@ -271,10 +271,10 @@ should be visited too. When split inserts the downlink to the parent, it`
`271`	`271`	`clears the F_FOLLOW_RIGHT flag in the child, and sets the NSN field in the`
`272`	`272`	`child page header to match the LSN of the insertion on the parent. If the`
`273`	`273`	`F_FOLLOW_RIGHT flag is not set, a scan compares the NSN on the child and the`
`274`		`-LSN it saw in the parent. IfNSN < LSN, the scan looked attheparent page`
`275`		`-beforethedownlink was inserted, so it should follow therightlink. Otherwise`
`276`		`-the scan saw the downlink intheparent page, and will/did follow that as`
`277`		`-usual.`
	`274`	`+LSN it saw in the parent. Ifthe child's NSN is greater thantheLSN seen on`
	`275`	`+the parent,thescan looked at the parent page before thedownlink was`
	`276`	`+inserted, so it should followtherightlink. Otherwise the scan saw the`
	`277`	`+downlink in the parent page, and will/did follow that asusual.`
`278`	`278`
`279`	`279`	`A scan can't normally see a page with the F_FOLLOW_RIGHT flag set, because`
`280`	`280`	`a page split keeps the child pages locked until the downlink has been inserted`

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