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Commit6394a3a

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Move MAX_BACKENDS to procnumber.h
MAX_BACKENDS influences many things besides postmaster. I e.g. noticed that wedon't have static assertions ensuring BUF_REFCOUNT_MASK is big enough forMAX_BACKENDS, adding them would require including postmaster.h inbuf_internals.h which doesn't seem right.While at that, add MAX_BACKENDS_BITS, as that's useful in various places forstatic assertions (to be added in subsequent commits).Reviewed-by: Thomas Munro <thomas.munro@gmail.com>Discussion:https://postgr.es/m/wptizm4qt6yikgm2pt52xzyv6ycmqiutloyvypvmagn7xvqkce@d4xuv3mylpg4
1 parent0600d27 commit6394a3a

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6 files changed

+17
-14
lines changed

6 files changed

+17
-14
lines changed

‎src/backend/storage/lmgr/lwlock.c

Lines changed: 1 addition & 1 deletion
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@@ -80,9 +80,9 @@
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#include"pg_trace.h"
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#include"pgstat.h"
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#include"port/pg_bitutils.h"
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#include"postmaster/postmaster.h"
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#include"storage/proc.h"
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#include"storage/proclist.h"
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#include"storage/procnumber.h"
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#include"storage/spin.h"
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#include"utils/memutils.h"
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‎src/backend/utils/adt/xid8funcs.c

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@@ -32,9 +32,9 @@
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#include"lib/qunique.h"
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#include"libpq/pqformat.h"
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#include"miscadmin.h"
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#include"postmaster/postmaster.h"
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#include"storage/lwlock.h"
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#include"storage/procarray.h"
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#include"storage/procnumber.h"
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#include"utils/builtins.h"
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#include"utils/memutils.h"
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#include"utils/snapmgr.h"

‎src/backend/utils/init/postinit.c

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@@ -49,6 +49,7 @@
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#include"storage/lmgr.h"
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#include"storage/proc.h"
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#include"storage/procarray.h"
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#include"storage/procnumber.h"
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#include"storage/procsignal.h"
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#include"storage/sinvaladt.h"
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#include"storage/smgr.h"

‎src/backend/utils/misc/guc_tables.c

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@@ -77,6 +77,7 @@
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#include"storage/large_object.h"
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#include"storage/pg_shmem.h"
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#include"storage/predicate.h"
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#include"storage/procnumber.h"
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#include"storage/standby.h"
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#include"tcop/backend_startup.h"
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#include"tcop/tcopprot.h"

‎src/include/postmaster/postmaster.h

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@@ -126,18 +126,6 @@ extern PMChild *AllocDeadEndChild(void);
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externboolReleasePostmasterChildSlot(PMChild*pmchild);
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externPMChild*FindPostmasterChildByPid(intpid);
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/*
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* Note: MAX_BACKENDS is limited to 2^18-1 because that's the width reserved
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* for buffer references in buf_internals.h. This limitation could be lifted
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* by using a 64bit state; but it's unlikely to be worthwhile as 2^18-1
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* backends exceed currently realistic configurations. Even if that limitation
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* were removed, we still could not a) exceed 2^23-1 because inval.c stores
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* the ProcNumber as a 3-byte signed integer, b) INT_MAX/4 because some places
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* compute 4*MaxBackends without any overflow check. This is rechecked in the
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* relevant GUC check hooks and in RegisterBackgroundWorker().
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*/
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#defineMAX_BACKENDS0x3FFFF
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/*
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* These values correspond to the special must-be-first options for dispatching
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* to various subprograms. parse_dispatch_option() can be used to convert an

‎src/include/storage/procnumber.h

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Original file line numberDiff line numberDiff line change
@@ -25,6 +25,19 @@ typedef int ProcNumber;
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#defineINVALID_PROC_NUMBER(-1)
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/*
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* Note: MAX_BACKENDS_BITS is 18 as that is the space available for buffer
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* refcounts in buf_internals.h. This limitation could be lifted by using a
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* 64bit state; but it's unlikely to be worthwhile as 2^18-1 backends exceed
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* currently realistic configurations. Even if that limitation were removed,
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* we still could not a) exceed 2^23-1 because inval.c stores the ProcNumber
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* as a 3-byte signed integer, b) INT_MAX/4 because some places compute
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* 4*MaxBackends without any overflow check. This is rechecked in the
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* relevant GUC check hooks and in RegisterBackgroundWorker().
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*/
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#defineMAX_BACKENDS_BITS18
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#defineMAX_BACKENDS((1U << MAX_BACKENDS_BITS)-1)
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/*
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* Proc number of this backend (same as GetNumberFromPGProc(MyProc))
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*/

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