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Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/transam/README | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README index f8ebf5758f0..548ddbb4dd5 100644 --- a/src/backend/access/transam/README +++ b/src/backend/access/transam/README @@ -564,6 +564,14 @@ something like if (BufferIsValid(buffer0)) UnlockReleaseBuffer(buffer0); +Note that we must only use PageSetLSN/PageGetLSN() when we know the action +is serialised. Only Startup process may modify data blocks during recovery, +so Startup process may execute PageGetLSN() without fear of serialisation +problems. All other processes must only call PageSet/GetLSN when holding +either an exclusive buffer lock or a shared lock plus buffer header lock, +or be writing the data block directly rather than through shared buffers +while holding AccessExclusiveLock on the relation. + Due to all these constraints, complex changes (such as a multilevel index insertion) normally need to be described by a series of atomic-action WAL records. What do you do if the intermediate states are not self-consistent? |