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Commit89f2b64

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Initialize random() in bootstrap/stand-alone postgres and in initdb.
This removes a difference between the standard IsUnderPostmasterexecution environment and that of --boot and --single. In a stand-alonebackend, "SELECT random()" always started at the same seed.On a system capable of using posix shared memory, initdb could stillconclude "selecting dynamic shared memory implementation ... sysv".Crashed --boot or --single postgres processes orphaned shared memoryobjects having names that collided with the not-actually-random namesthat initdb probed. The sysv fallback appeared after ten crashes of--boot or --single postgres. Since --boot and --single are rare inproduction use, systems used for PostgreSQL development are theprincipal candidate to notice this symptom.Back-patch to 9.3 (all supported versions). PostgreSQL 9.4 introduceddynamic shared memory, but 9.3 does share the "SELECT random()" problem.Reviewed by Tom Lane and Kyotaro HORIGUCHI.Discussion:https://postgr.es/m/20180915221546.GA3159382@rfd.leadboat.com
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‎src/backend/utils/init/miscinit.c

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@@ -320,6 +320,14 @@ InitStandaloneProcess(const char *argv0)
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MyStartTime=time(NULL);/* set our start time in case we call elog */
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/*
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* Initialize random() for the first time, like PostmasterMain() would.
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* In a regular IsUnderPostmaster backend, BackendRun() computes a
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* high-entropy seed before any user query. Fewer distinct initial seeds
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* can occur here.
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*/
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srandom((unsignedint) (MyProcPid ^MyStartTime));
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/* Initialize process-local latch support */
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InitializeLatchSupport();
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MyLatch=&LocalLatchData;

‎src/bin/initdb/initdb.c

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@@ -922,6 +922,9 @@ choose_dsm_implementation(void)
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#ifdefHAVE_SHM_OPEN
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intntries=10;
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/* Initialize random(); this function is its only user in this program. */
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srandom((unsignedint) (getpid() ^time(NULL)));
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while (ntries>0)
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{
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uint32handle;

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