diff options
Diffstat (limited to 'src/backend/access/transam/xlog.c')
| -rw-r--r-- | src/backend/access/transam/xlog.c | 60 |
1 files changed, 34 insertions, 26 deletions
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9d96044cbdc..41800a46040 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -971,19 +971,6 @@ begin:; } /* - * If we backed up any full blocks and online backup is not in progress, - * mark the backup blocks as removable. This allows the WAL archiver to - * know whether it is safe to compress archived WAL data by transforming - * full-block records into the non-full-block format. - * - * Note: we could just set the flag whenever !forcePageWrites, but - * defining it like this leaves the info bit free for some potential other - * use in records without any backup blocks. - */ - if ((info & XLR_BKP_BLOCK_MASK) && !Insert->forcePageWrites) - info |= XLR_BKP_REMOVABLE; - - /* * If there isn't enough space on the current XLOG page for a record * header, advance to the next page (leaving the unused space as zeroes). */ @@ -1602,6 +1589,21 @@ AdvanceXLInsertBuffer(bool new_segment) NewPage ->xlp_pageaddr.xrecoff = NewPageEndPtr.xrecoff - XLOG_BLCKSZ; /* + * If online backup is not in progress, mark the header to indicate that + * WAL records beginning in this page have removable backup blocks. This + * allows the WAL archiver to know whether it is safe to compress archived + * WAL data by transforming full-block records into the non-full-block + * format. It is sufficient to record this at the page level because we + * force a page switch (in fact a segment switch) when starting a backup, + * so the flag will be off before any records can be written during the + * backup. At the end of a backup, the last page will be marked as all + * unsafe when perhaps only part is unsafe, but at worst the archiver + * would miss the opportunity to compress a few records. + */ + if (!Insert->forcePageWrites) + NewPage->xlp_info |= XLP_BKP_REMOVABLE; + + /* * If first page of an XLOG segment file, make it a long header. */ if ((NewPage->xlp_pageaddr.xrecoff % XLogSegSize) == 0) @@ -8850,19 +8852,6 @@ do_pg_start_backup(const char *backupidstr, bool fast, char **labelfile) MAXPGPATH))); /* - * Force an XLOG file switch before the checkpoint, to ensure that the WAL - * segment the checkpoint is written to doesn't contain pages with old - * timeline IDs. That would otherwise happen if you called - * pg_start_backup() right after restoring from a PITR archive: the first - * WAL segment containing the startup checkpoint has pages in the - * beginning with the old timeline ID. That can cause trouble at recovery: - * we won't have a history file covering the old timeline if pg_xlog - * directory was not included in the base backup and the WAL archive was - * cleared too before starting the backup. - */ - RequestXLogSwitch(); - - /* * Mark backup active in shared memory. We must do full-page WAL writes * during an on-line backup even if not doing so at other times, because * it's quite possible for the backup dump to obtain a "torn" (partially @@ -8902,6 +8891,25 @@ do_pg_start_backup(const char *backupidstr, bool fast, char **labelfile) { bool gotUniqueStartpoint = false; + /* + * Force an XLOG file switch before the checkpoint, to ensure that the + * WAL segment the checkpoint is written to doesn't contain pages with + * old timeline IDs. That would otherwise happen if you called + * pg_start_backup() right after restoring from a PITR archive: the + * first WAL segment containing the startup checkpoint has pages in + * the beginning with the old timeline ID. That can cause trouble at + * recovery: we won't have a history file covering the old timeline if + * pg_xlog directory was not included in the base backup and the WAL + * archive was cleared too before starting the backup. + * + * This also ensures that we have emitted a WAL page header that has + * XLP_BKP_REMOVABLE off before we emit the checkpoint record. + * Therefore, if a WAL archiver (such as pglesslog) is trying to + * compress out removable backup blocks, it won't remove any that + * occur after this point. + */ + RequestXLogSwitch(); + do { /* |