Commitd9fe702

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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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Lines changed: 10 additions & 8 deletions

Original file line number	Diff line number	Diff line change
`@@ -1332,14 +1332,6 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)`
`1332`	`1332`	`pcxt=CreateParallelContext("postgres","_bt_parallel_build_main",`
`1333`	`1333`	`request);`
`1334`	`1334`
`1335`		`-/* If no DSM segment was available, back out (do serial build) */`
`1336`		`-if (pcxt->seg==NULL)`
`1337`		`-{`
`1338`		`-DestroyParallelContext(pcxt);`
`1339`		`-ExitParallelMode();`
`1340`		`-return;`
`1341`		`-}`
`1342`		`-`
`1343`	`1335`	`scantuplesortstates=leaderparticipates ?request+1 :request;`
`1344`	`1336`
`1345`	`1337`	`/*`
`@@ -1383,6 +1375,16 @@ _bt_begin_parallel(BTBuildState *buildstate, bool isconcurrent, int request)`
`1383`	`1375`	`/* Everyone's had a chance to ask for space, so now create the DSM */`
`1384`	`1376`	`InitializeParallelDSM(pcxt);`
`1385`	`1377`
	`1378`	`+/* If no DSM segment was available, back out (do serial build) */`
	`1379`	`+if (pcxt->seg==NULL)`
	`1380`	`+{`
	`1381`	`+if (IsMVCCSnapshot(snapshot))`
	`1382`	`+UnregisterSnapshot(snapshot);`
	`1383`	`+DestroyParallelContext(pcxt);`
	`1384`	`+ExitParallelMode();`
	`1385`	`+return;`
	`1386`	`+}`
	`1387`	`+`
`1386`	`1388`	`/* Store shared build state, for which we reserved space */`
`1387`	`1389`	`btshared= (BTShared*)shm_toc_allocate(pcxt->toc,estbtshared);`
`1388`	`1390`	`/* Initialize immutable state */`

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