57 lines
2.1 KiB
C
57 lines
2.1 KiB
C
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/*-------------------------------------------------------------------------
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*
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* procnumber.h
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* definition of process number
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*
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*
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* Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/storage/procnumber.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef PROCNUMBER_H
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#define PROCNUMBER_H
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/*
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* ProcNumber uniquely identifies an active backend or auxiliary process.
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* It's assigned at backend startup after authentication, when the process
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* adds itself to the proc array. It is an index into the proc array,
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* starting from 0. Note that a ProcNumber can be reused for a different
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* backend immediately after a backend exits.
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*/
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typedef int ProcNumber;
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#define INVALID_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. We check that the configured
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* number of backends does not exceed MAX_BACKENDS in InitializeMaxBackends().
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*/
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#define MAX_BACKENDS_BITS 18
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#define MAX_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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extern PGDLLIMPORT ProcNumber MyProcNumber;
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/* proc number of our parallel session leader, or INVALID_PROC_NUMBER if none */
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extern PGDLLIMPORT ProcNumber ParallelLeaderProcNumber;
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/*
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* The ProcNumber to use for our session's temp relations is normally our own,
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* but parallel workers should use their leader's proc number.
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*/
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#define ProcNumberForTempRelations() \
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(ParallelLeaderProcNumber == INVALID_PROC_NUMBER ? MyProcNumber : ParallelLeaderProcNumber)
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#endif /* PROCNUMBER_H */
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