diff options
Diffstat (limited to 'src/include/postmaster/postmaster.h')
| -rw-r--r-- | src/include/postmaster/postmaster.h | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h index 61e3060c9fd..b2d7776f2a8 100644 --- a/src/include/postmaster/postmaster.h +++ b/src/include/postmaster/postmaster.h @@ -63,12 +63,15 @@ extern void ShmemBackendArrayAllocation(void); #endif /* - * Note: MAX_BACKENDS is limited to 2^23-1 because inval.c stores the - * backend ID as a 3-byte signed integer. Even if that limitation were - * removed, we still could not exceed INT_MAX/4 because some places compute - * 4*MaxBackends without any overflow check. This is rechecked in the relevant - * GUC check hooks and in RegisterBackgroundWorker(). + * Note: MAX_BACKENDS is limited to 2^18-1 because that's the width reserved + * for buffer references in buf_internals.h. This limitation could be lifted + * by using a 64bit state; but it's unlikely to be worthwhile as 2^18-1 + * backends exceed currently realistic configurations. Even if that limitation + * were removed, we still could not a) exceed 2^23-1 because inval.c stores + * the backend ID as a 3-byte signed integer, b) INT_MAX/4 because some places + * compute 4*MaxBackends without any overflow check. This is rechecked in the + * relevant GUC check hooks and in RegisterBackgroundWorker(). */ -#define MAX_BACKENDS 0x7fffff +#define MAX_BACKENDS 0x3FFFF #endif /* _POSTMASTER_H */ |