Commitf37ff03

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Refactor confusing code in _mdfd_openseg().

As reported independently by a couple of people, _mdfd_openseg() is coded in away that seems to imply that the segments could be opened in an order thatisn't strictly sequential. Even if that were true, it's also using the wrongcomparison. It's not an active bug, since the condition is always true anyway,but it's confusing, so replace it with an assertion.Author: Thomas MunroReviewed-by: Andres Freund, Kyotaro Horiguchi, Noah MischDiscussion:https://postgr.es/m/CA%2BhUKG%2BNBw%2BuSzxF1os-SO6gUuw%3DcqO5DAybk6KnHKzgGvxhxA%40mail.gmail.comDiscussion:https://postgr.es/m/20191222091930.GA1280238%40rfd.leadboat.com

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Lines changed: 7 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -1100,8 +1100,13 @@ _mdfd_openseg(SMgrRelation reln, ForkNumber forknum, BlockNumber segno,`
`1100`	`1100`	`if (fd<0)`
`1101`	`1101`	`returnNULL;`
`1102`	`1102`
`1103`		`-if (segno <=reln->md_num_open_segs[forknum])`
`1104`		`-_fdvec_resize(reln,forknum,segno+1);`
	`1103`	`+/*`
	`1104`	`+ * Segments are always opened in order from lowest to highest, so we must`
	`1105`	`+ * be adding a new one at the end.`
	`1106`	`+ */`
	`1107`	`+Assert(segno==reln->md_num_open_segs[forknum]);`
	`1108`	`+`
	`1109`	`+_fdvec_resize(reln,forknum,segno+1);`
`1105`	`1110`
`1106`	`1111`	`/* fill the entry */`
`1107`	`1112`	`v=&reln->md_seg_fds[forknum][segno];`

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