On Wed, Nov 16, 2016 at 11:45 AM, Robert Haas <[email protected]> wrote:
> The header comment for heap_create_init_fork() says this:
>
> /*
> * Set up an init fork for an unlogged table so that it can be correctly
> * reinitialized on restart. Since we're going to do an immediate sync, we
> * only need to xlog this if archiving or streaming is enabled. And the
> * immediate sync is required, because otherwise there's no guarantee that
> * this will hit the disk before the next checkpoint moves the redo pointer.
> */
>
> Your patch causes the code not to match the comment any more. And the
> comment explains why at the time I wrote this code I thought it was OK
> to have the XLogIsNeeded() test in there, so it clearly needs
> updating.
Indeed I missed this comment block. Please let me suggest the following instead:
/*
* Set up an init fork for an unlogged table so that it can be correctly
- * reinitialized on restart. Since we're going to do an immediate sync, we
- * only need to xlog this if archiving or streaming is enabled. And the
- * immediate sync is required, because otherwise there's no guarantee that
- * this will hit the disk before the next checkpoint moves the redo pointer.
+ * reinitialized on restart. An immediate sync is required even if the
+ * page has been logged, because the write did not go through
+ * shared_buffers and therefore a concurrent checkpoint may have moved
+ * the redo pointer past our xlog record.
*/
--
Michael
diff --git a/contrib/bloom/blinsert.c b/contrib/bloom/blinsert.c
index 0946aa2..c9c7049 100644
--- a/contrib/bloom/blinsert.c
+++ b/contrib/bloom/blinsert.c
@@ -164,13 +164,12 @@ blbuildempty(Relation index)
metapage = (Page) palloc(BLCKSZ);
BloomFillMetapage(index, metapage);
- /* Write the page. If archiving/streaming, XLOG it. */
+ /* Write the page and log it. */
PageSetChecksumInplace(metapage, BLOOM_METAPAGE_BLKNO);
smgrwrite(index->rd_smgr, INIT_FORKNUM, BLOOM_METAPAGE_BLKNO,
(char *) metapage, true);
- if (XLogIsNeeded())
- log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
- BLOOM_METAPAGE_BLKNO, metapage, false);
+ log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
+ BLOOM_METAPAGE_BLKNO, metapage, false);
/*
* An immediate sync is required even if we xlog'd the page, because the
diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 128744c..624aa84 100644
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -242,13 +242,12 @@ btbuildempty(Relation index)
metapage = (Page) palloc(BLCKSZ);
_bt_initmetapage(metapage, P_NONE, 0);
- /* Write the page. If archiving/streaming, XLOG it. */
+ /* Write the page and log it */
PageSetChecksumInplace(metapage, BTREE_METAPAGE);
smgrwrite(index->rd_smgr, INIT_FORKNUM, BTREE_METAPAGE,
(char *) metapage, true);
- if (XLogIsNeeded())
- log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
- BTREE_METAPAGE, metapage, false);
+ log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
+ BTREE_METAPAGE, metapage, false);
/*
* An immediate sync is required even if we xlog'd the page, because the
diff --git a/src/backend/access/spgist/spginsert.c b/src/backend/access/spgist/spginsert.c
index 01c8d21..8ac3b00 100644
--- a/src/backend/access/spgist/spginsert.c
+++ b/src/backend/access/spgist/spginsert.c
@@ -161,13 +161,12 @@ spgbuildempty(Relation index)
page = (Page) palloc(BLCKSZ);
SpGistInitMetapage(page);
- /* Write the page. If archiving/streaming, XLOG it. */
+ /* Write the page and log it. */
PageSetChecksumInplace(page, SPGIST_METAPAGE_BLKNO);
smgrwrite(index->rd_smgr, INIT_FORKNUM, SPGIST_METAPAGE_BLKNO,
(char *) page, true);
- if (XLogIsNeeded())
- log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
- SPGIST_METAPAGE_BLKNO, page, false);
+ log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
+ SPGIST_METAPAGE_BLKNO, page, false);
/* Likewise for the root page. */
SpGistInitPage(page, SPGIST_LEAF);
@@ -175,9 +174,8 @@ spgbuildempty(Relation index)
PageSetChecksumInplace(page, SPGIST_ROOT_BLKNO);
smgrwrite(index->rd_smgr, INIT_FORKNUM, SPGIST_ROOT_BLKNO,
(char *) page, true);
- if (XLogIsNeeded())
- log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
- SPGIST_ROOT_BLKNO, page, true);
+ log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
+ SPGIST_ROOT_BLKNO, page, true);
/* Likewise for the null-tuples root page. */
SpGistInitPage(page, SPGIST_LEAF | SPGIST_NULLS);
@@ -185,9 +183,8 @@ spgbuildempty(Relation index)
PageSetChecksumInplace(page, SPGIST_NULL_BLKNO);
smgrwrite(index->rd_smgr, INIT_FORKNUM, SPGIST_NULL_BLKNO,
(char *) page, true);
- if (XLogIsNeeded())
- log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
- SPGIST_NULL_BLKNO, page, true);
+ log_newpage(&index->rd_smgr->smgr_rnode.node, INIT_FORKNUM,
+ SPGIST_NULL_BLKNO, page, true);
/*
* An immediate sync is required even if we xlog'd the pages, because the
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 0cf7b9e..6cd7ce5 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -1370,18 +1370,17 @@ heap_create_with_catalog(const char *relname,
/*
* Set up an init fork for an unlogged table so that it can be correctly
- * reinitialized on restart. Since we're going to do an immediate sync, we
- * only need to xlog this if archiving or streaming is enabled. And the
- * immediate sync is required, because otherwise there's no guarantee that
- * this will hit the disk before the next checkpoint moves the redo pointer.
+ * reinitialized on restart. An immediate sync is required even if the
+ * page has been logged, because the write did not go through
+ * shared_buffers and therefore a concurrent checkpoint may have moved
+ * the redo pointer past our xlog record.
*/
void
heap_create_init_fork(Relation rel)
{
RelationOpenSmgr(rel);
smgrcreate(rel->rd_smgr, INIT_FORKNUM, false);
- if (XLogIsNeeded())
- log_smgrcreate(&rel->rd_smgr->smgr_rnode.node, INIT_FORKNUM);
+ log_smgrcreate(&rel->rd_smgr->smgr_rnode.node, INIT_FORKNUM);
smgrimmedsync(rel->rd_smgr, INIT_FORKNUM);
}
--
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