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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) 1996-2016, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/pg_config_manual.h
+ *------------------------------------------------------------------------
+ */
+
+/*
+ * Maximum length for identifiers (e.g. table names, column names,
+ * function names). Names actually are limited to one less 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
+
+/*
+ * Set the upper and lower bounds of sequence values.
+ */
+#define SEQ_MAXVALUE PG_INT64_MAX
+#define SEQ_MINVALUE (-SEQ_MAXVALUE)
+
+/*
+ * 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
+
+/*
+ * Define this if you want to allow the lo_import and lo_export SQL
+ * functions to be executed by ordinary users. By default these
+ * functions are only available to the Postgres superuser. CAUTION:
+ * These functions are SECURITY HOLES since they can read and write
+ * any file that the PostgreSQL server has permission to access. If
+ * you turn this on, don't say we didn't warn you.
+ */
+/* #define ALLOW_DANGEROUS_LO_FUNCTIONS */
+
+/*
+ * 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
+
+/*
+ * Disable UNIX sockets for certain operating systems.
+ */
+#if defined(WIN32)
+#undef HAVE_UNIX_SOCKETS
+#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.)
+ */
+#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. (Currently, only OpenSSL is supported, but we might add
+ * more implementations in the future.)
+ */
+#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.
+ */
+#define DEFAULT_PGSOCKET_DIR "/tmp"
+
+/*
+ * 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. See also
+ * src/tools/valgrind.supp. "make installcheck" runs 20-30x longer under
+ * Valgrind. Note that USE_VALGRIND slowed older versions of Valgrind by an
+ * additional order of magnitude; Valgrind 3.8.1 does not have this problem.
+ * The client requests fall in hot code paths, so USE_VALGRIND also slows
+ * native execution by a few percentage points.
+ *
+ * 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 */
+
+/*
+ * 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 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 */
+
+/*
+ * Other debug #defines (documentation, anyone?)
+ */
+/* #define HEAPDEBUGALL */
+/* #define ACLDEBUG */