Commit2e2351b

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Handle lack of DSM slots in parallel btree build, take 2.

Commit74618e7 added a new check intended to fix a bug, but putit in the wrong place so that parallel btree build was alwaysdisabled. Do the check after we've actually tried to createa DSM segment. Back-patch to 11, like the earlier commit.Reviewed-by: Peter GeogheganDiscussion:https://postgr.es/m/CAH2-WzmDABkJzrNnvf%2BOULK-_A_j9gkYg_Dz-H62jzNv4eKQTw%40mail.gmail.com

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+10

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Lines changed: 10 additions & 8 deletions

Original file line number	Diff line number	Diff line change
`@@ -1353,14 +1353,6 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)`
`1353`	`1353`	`pcxt=CreateParallelContext("postgres","_bt_parallel_build_main",`
`1354`	`1354`	`request);`
`1355`	`1355`
`1356`		`-/* If no DSM segment was available, back out (do serial build) */`
`1357`		`-if (pcxt->seg==NULL)`
`1358`		`-{`
`1359`		`-DestroyParallelContext(pcxt);`
`1360`		`-ExitParallelMode();`
`1361`		`-return;`
`1362`		`-}`
`1363`		`-`
`1364`	`1356`	`scantuplesortstates=leaderparticipates ?request+1 :request;`
`1365`	`1357`
`1366`	`1358`	`/*`
`@@ -1404,6 +1396,16 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)`
`1404`	`1396`	`/* Everyone's had a chance to ask for space, so now create the DSM */`
`1405`	`1397`	`InitializeParallelDSM(pcxt);`
`1406`	`1398`
	`1399`	`+/* If no DSM segment was available, back out (do serial build) */`
	`1400`	`+if (pcxt->seg==NULL)`
	`1401`	`+{`
	`1402`	`+if (IsMVCCSnapshot(snapshot))`
	`1403`	`+UnregisterSnapshot(snapshot);`
	`1404`	`+DestroyParallelContext(pcxt);`
	`1405`	`+ExitParallelMode();`
	`1406`	`+return;`
	`1407`	`+}`
	`1408`	`+`
`1407`	`1409`	`/* Store shared build state, for which we reserved space */`
`1408`	`1410`	`btshared= (BTShared*)shm_toc_allocate(pcxt->toc,estbtshared);`
`1409`	`1411`	`/* Initialize immutable state */`

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