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db_include/pg_config_manual.h

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+/*------------------------------------------------------------------------
+ * PostgreSQL manual configuration settings
+ *
+ * This file contains various configuration symbols and limits.  In
+ * all cases, changing them is only useful in very rare situations or
+ * for developers.  If you edit any of these, be sure to do a *full*
+ * rebuild (and an initdb if noted).
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/pg_config_manual.h
+ *------------------------------------------------------------------------
+ */
+
+/*
+ * This is the default value for wal_segment_size to be used when initdb is run
+ * without the --wal-segsize option.  It must be a valid segment size.
+ */
+#define DEFAULT_XLOG_SEG_SIZE	(16*1024*1024)
+
+/*
+ * Maximum length for identifiers (e.g. table names, column names,
+ * function names).  Names actually are limited to one fewer byte than this,
+ * because the length must include a trailing zero byte.
+ *
+ * Changing this requires an initdb.
+ */
+#define NAMEDATALEN 64
+
+/*
+ * Maximum number of arguments to a function.
+ *
+ * The minimum value is 8 (GIN indexes use 8-argument support functions).
+ * The maximum possible value is around 600 (limited by index tuple size in
+ * pg_proc's index; BLCKSZ larger than 8K would allow more).  Values larger
+ * than needed will waste memory and processing time, but do not directly
+ * cost disk space.
+ *
+ * Changing this does not require an initdb, but it does require a full
+ * backend recompile (including any user-defined C functions).
+ */
+#define FUNC_MAX_ARGS		100
+
+/*
+ * Maximum number of columns in an index.  There is little point in making
+ * this anything but a multiple of 32, because the main cost is associated
+ * with index tuple header size (see access/itup.h).
+ *
+ * Changing this requires an initdb.
+ */
+#define INDEX_MAX_KEYS		32
+
+/*
+ * Maximum number of columns in a partition key
+ */
+#define PARTITION_MAX_KEYS	32
+
+/*
+ * Decide whether built-in 8-byte types, including float8, int8, and
+ * timestamp, are passed by value.  This is on by default if sizeof(Datum) >=
+ * 8 (that is, on 64-bit platforms).  If sizeof(Datum) < 8 (32-bit platforms),
+ * this must be off.  We keep this here as an option so that it is easy to
+ * test the pass-by-reference code paths on 64-bit platforms.
+ *
+ * Changing this requires an initdb.
+ */
+#if SIZEOF_VOID_P >= 8
+#define USE_FLOAT8_BYVAL 1
+#endif
+
+/*
+ * When we don't have native spinlocks, we use semaphores to simulate them.
+ * Decreasing this value reduces consumption of OS resources; increasing it
+ * may improve performance, but supplying a real spinlock implementation is
+ * probably far better.
+ */
+#define NUM_SPINLOCK_SEMAPHORES		128
+
+/*
+ * When we have neither spinlocks nor atomic operations support we're
+ * implementing atomic operations on top of spinlock on top of semaphores. To
+ * be safe against atomic operations while holding a spinlock separate
+ * semaphores have to be used.
+ */
+#define NUM_ATOMICS_SEMAPHORES		64
+
+/*
+ * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
+ * maximum usable pathname length is one less).
+ *
+ * We'd use a standard system header symbol for this, if there weren't
+ * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
+ * defined by different "standards", and often have different values
+ * on the same platform!  So we just punt and use a reasonably
+ * generous setting here.
+ */
+#define MAXPGPATH		1024
+
+/*
+ * PG_SOMAXCONN: maximum accept-queue length limit passed to
+ * listen(2).  You'd think we should use SOMAXCONN from
+ * <sys/socket.h>, but on many systems that symbol is much smaller
+ * than the kernel's actual limit.  In any case, this symbol need be
+ * twiddled only if you have a kernel that refuses large limit values,
+ * rather than silently reducing the value to what it can handle
+ * (which is what most if not all Unixen do).
+ */
+#define PG_SOMAXCONN	10000
+
+/*
+ * You can try changing this if you have a machine with bytes of
+ * another size, but no guarantee...
+ */
+#define BITS_PER_BYTE		8
+
+/*
+ * Preferred alignment for disk I/O buffers.  On some CPUs, copies between
+ * user space and kernel space are significantly faster if the user buffer
+ * is aligned on a larger-than-MAXALIGN boundary.  Ideally this should be
+ * a platform-dependent value, but for now we just hard-wire it.
+ */
+#define ALIGNOF_BUFFER	32
+
+/*
+ * If EXEC_BACKEND is defined, the postmaster uses an alternative method for
+ * starting subprocesses: Instead of simply using fork(), as is standard on
+ * Unix platforms, it uses fork()+exec() or something equivalent on Windows,
+ * as well as lots of extra code to bring the required global state to those
+ * new processes.  This must be enabled on Windows (because there is no
+ * fork()).  On other platforms, it's only useful for verifying those
+ * otherwise Windows-specific code paths.
+ */
+#if defined(WIN32) && !defined(__CYGWIN__)
+#define EXEC_BACKEND
+#endif
+
+/*
+ * Define this if your operating system supports link()
+ */
+#if !defined(WIN32) && !defined(__CYGWIN__)
+#define HAVE_WORKING_LINK 1
+#endif
+
+/*
+ * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
+ * posix_fadvise() kernel call.  Usually the automatic configure tests are
+ * sufficient, but some older Linux distributions had broken versions of
+ * posix_fadvise().  If necessary you can remove the #define here.
+ */
+#if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
+#define USE_POSIX_FADVISE
+#endif
+
+/*
+ * USE_PREFETCH code should be compiled only if we have a way to implement
+ * prefetching.  (This is decoupled from USE_POSIX_FADVISE because there
+ * might in future be support for alternative low-level prefetch APIs.
+ * If you change this, you probably need to adjust the error message in
+ * check_effective_io_concurrency.)
+ */
+#ifdef USE_POSIX_FADVISE
+#define USE_PREFETCH
+#endif
+
+/*
+ * Default and maximum values for backend_flush_after, bgwriter_flush_after
+ * and checkpoint_flush_after; measured in blocks.  Currently, these are
+ * enabled by default if sync_file_range() exists, ie, only on Linux.  Perhaps
+ * we could also enable by default if we have mmap and msync(MS_ASYNC)?
+ */
+#ifdef HAVE_SYNC_FILE_RANGE
+#define DEFAULT_BACKEND_FLUSH_AFTER 0	/* never enabled by default */
+#define DEFAULT_BGWRITER_FLUSH_AFTER 64
+#define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
+#else
+#define DEFAULT_BACKEND_FLUSH_AFTER 0
+#define DEFAULT_BGWRITER_FLUSH_AFTER 0
+#define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
+#endif
+/* upper limit for all three variables */
+#define WRITEBACK_MAX_PENDING_FLUSHES 256
+
+/*
+ * USE_SSL code should be compiled only when compiling with an SSL
+ * implementation.
+ */
+#ifdef USE_OPENSSL
+#define USE_SSL
+#endif
+
+/*
+ * This is the default directory in which AF_UNIX socket files are
+ * placed.  Caution: changing this risks breaking your existing client
+ * applications, which are likely to continue to look in the old
+ * directory.  But if you just hate the idea of sockets in /tmp,
+ * here's where to twiddle it.  You can also override this at runtime
+ * with the postmaster's -k switch.
+ *
+ * If set to an empty string, then AF_UNIX sockets are not used by default: A
+ * server will not create an AF_UNIX socket unless the run-time configuration
+ * is changed, a client will connect via TCP/IP by default and will only use
+ * an AF_UNIX socket if one is explicitly specified.
+ *
+ * This is done by default on Windows because there is no good standard
+ * location for AF_UNIX sockets and many installations on Windows don't
+ * support them yet.
+ */
+#ifndef WIN32
+#define DEFAULT_PGSOCKET_DIR  "/tmp"
+#else
+#define DEFAULT_PGSOCKET_DIR ""
+#endif
+
+/*
+ * This is the default event source for Windows event log.
+ */
+#define DEFAULT_EVENT_SOURCE  "PostgreSQL"
+
+/*
+ * The random() function is expected to yield values between 0 and
+ * MAX_RANDOM_VALUE.  Currently, all known implementations yield
+ * 0..2^31-1, so we just hardwire this constant.  We could do a
+ * configure test if it proves to be necessary.  CAUTION: Think not to
+ * replace this with RAND_MAX.  RAND_MAX defines the maximum value of
+ * the older rand() function, which is often different from --- and
+ * considerably inferior to --- random().
+ */
+#define MAX_RANDOM_VALUE  PG_INT32_MAX
+
+/*
+ * On PPC machines, decide whether to use the mutex hint bit in LWARX
+ * instructions.  Setting the hint bit will slightly improve spinlock
+ * performance on POWER6 and later machines, but does nothing before that,
+ * and will result in illegal-instruction failures on some pre-POWER4
+ * machines.  By default we use the hint bit when building for 64-bit PPC,
+ * which should be safe in nearly all cases.  You might want to override
+ * this if you are building 32-bit code for a known-recent PPC machine.
+ */
+#ifdef HAVE_PPC_LWARX_MUTEX_HINT	/* must have assembler support in any case */
+#if defined(__ppc64__) || defined(__powerpc64__)
+#define USE_PPC_LWARX_MUTEX_HINT
+#endif
+#endif
+
+/*
+ * On PPC machines, decide whether to use LWSYNC instructions in place of
+ * ISYNC and SYNC.  This provides slightly better performance, but will
+ * result in illegal-instruction failures on some pre-POWER4 machines.
+ * By default we use LWSYNC when building for 64-bit PPC, which should be
+ * safe in nearly all cases.
+ */
+#if defined(__ppc64__) || defined(__powerpc64__)
+#define USE_PPC_LWSYNC
+#endif
+
+/*
+ * Assumed cache line size. This doesn't affect correctness, but can be used
+ * for low-level optimizations. Currently, this is used to pad some data
+ * structures in xlog.c, to ensure that highly-contended fields are on
+ * different cache lines. Too small a value can hurt performance due to false
+ * sharing, while the only downside of too large a value is a few bytes of
+ * wasted memory. The default is 128, which should be large enough for all
+ * supported platforms.
+ */
+#define PG_CACHE_LINE_SIZE		128
+
+/*
+ *------------------------------------------------------------------------
+ * The following symbols are for enabling debugging code, not for
+ * controlling user-visible features or resource limits.
+ *------------------------------------------------------------------------
+ */
+
+/*
+ * Include Valgrind "client requests", mostly in the memory allocator, so
+ * Valgrind understands PostgreSQL memory contexts.  This permits detecting
+ * memory errors that Valgrind would not detect on a vanilla build.  It also
+ * enables detection of buffer accesses that take place without holding a
+ * buffer pin (or without holding a buffer lock in the case of index access
+ * methods that superimpose their own custom client requests on top of the
+ * generic bufmgr.c requests).
+ *
+ * "make installcheck" is significantly slower under Valgrind.  The client
+ * requests fall in hot code paths, so USE_VALGRIND slows execution by a few
+ * percentage points even when not run under Valgrind.
+ *
+ * Do not try to test the server under Valgrind without having built the
+ * server with USE_VALGRIND; else you will get false positives from sinval
+ * messaging (see comments in AddCatcacheInvalidationMessage).  It's also
+ * important to use the suppression file src/tools/valgrind.supp to
+ * exclude other known false positives.
+ *
+ * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
+ * instrumentation of repalloc() is inferior without it.
+ */
+/* #define USE_VALGRIND */
+
+/*
+ * Define this to cause pfree()'d memory to be cleared immediately, to
+ * facilitate catching bugs that refer to already-freed values.
+ * Right now, this gets defined automatically if --enable-cassert.
+ */
+#ifdef USE_ASSERT_CHECKING
+#define CLOBBER_FREED_MEMORY
+#endif
+
+/*
+ * Define this to check memory allocation errors (scribbling on more
+ * bytes than were allocated).  Right now, this gets defined
+ * automatically if --enable-cassert or USE_VALGRIND.
+ */
+#if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
+#define MEMORY_CONTEXT_CHECKING
+#endif
+
+/*
+ * Define this to cause palloc()'d memory to be filled with random data, to
+ * facilitate catching code that depends on the contents of uninitialized
+ * memory.  Caution: this is horrendously expensive.
+ */
+/* #define RANDOMIZE_ALLOCATED_MEMORY */
+
+/*
+ * For cache-invalidation debugging, define DISCARD_CACHES_ENABLED to enable
+ * use of the debug_discard_caches GUC to aggressively flush syscache/relcache
+ * entries whenever it's possible to deliver invalidations.  See
+ * AcceptInvalidationMessages() in src/backend/utils/cache/inval.c for
+ * details.
+ *
+ * USE_ASSERT_CHECKING builds default to enabling this.  It's possible to use
+ * DISCARD_CACHES_ENABLED without a cassert build and the implied
+ * CLOBBER_FREED_MEMORY and MEMORY_CONTEXT_CHECKING options, but it's unlikely
+ * to be as effective at identifying problems.
+ */
+/* #define DISCARD_CACHES_ENABLED */
+
+#if defined(USE_ASSERT_CHECKING) && !defined(DISCARD_CACHES_ENABLED)
+#define DISCARD_CACHES_ENABLED
+#endif
+
+/*
+ * Backwards compatibility for the older compile-time-only clobber-cache
+ * macros.
+ */
+#if !defined(DISCARD_CACHES_ENABLED) && (defined(CLOBBER_CACHE_ALWAYS) || defined(CLOBBER_CACHE_RECURSIVELY))
+#define DISCARD_CACHES_ENABLED
+#endif
+
+/*
+ * Recover memory used for relcache entries when invalidated.  See
+ * RelationBuildDescr() in src/backend/utils/cache/relcache.c.
+ *
+ * This is active automatically for clobber-cache builds when clobbering is
+ * active, but can be overridden here by explicitly defining
+ * RECOVER_RELATION_BUILD_MEMORY.  Define to 1 to always free relation cache
+ * memory even when clobber is off, or to 0 to never free relation cache
+ * memory even when clobbering is on.
+ */
+ /* #define RECOVER_RELATION_BUILD_MEMORY 0 */	/* Force disable */
+ /* #define RECOVER_RELATION_BUILD_MEMORY 1 */	/* Force enable */
+
+/*
+ * Define this to force all parse and plan trees to be passed through
+ * copyObject(), to facilitate catching errors and omissions in
+ * copyObject().
+ */
+/* #define COPY_PARSE_PLAN_TREES */
+
+/*
+ * Define this to force all parse and plan trees to be passed through
+ * outfuncs.c/readfuncs.c, to facilitate catching errors and omissions in
+ * those modules.
+ */
+/* #define WRITE_READ_PARSE_PLAN_TREES */
+
+/*
+ * Define this to force all raw parse trees for DML statements to be scanned
+ * by raw_expression_tree_walker(), to facilitate catching errors and
+ * omissions in that function.
+ */
+/* #define RAW_EXPRESSION_COVERAGE_TEST */
+
+/*
+ * Enable debugging print statements for lock-related operations.
+ */
+/* #define LOCK_DEBUG */
+
+/*
+ * Enable debugging print statements for WAL-related operations; see
+ * also the wal_debug GUC var.
+ */
+/* #define WAL_DEBUG */
+
+/*
+ * Enable tracing of resource consumption during sort operations;
+ * see also the trace_sort GUC var.  For 8.1 this is enabled by default.
+ */
+#define TRACE_SORT 1
+
+/*
+ * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
+ */
+/* #define TRACE_SYNCSCAN */