1 /*------------------------------------------------------------------------
2 * PostgreSQL manual configuration settings
4 * This file contains various configuration symbols and limits. In
5 * all cases, changing them is only useful in very rare situations or
6 * for developers. If you edit any of these, be sure to do a *full*
7 * rebuild (and an initdb if noted).
9 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
10 * Portions Copyright (c) 1994, Regents of the University of California
12 * src/include/pg_config_manual.h
13 *------------------------------------------------------------------------
17 * Maximum length for identifiers (e.g. table names, column names,
18 * function names). Names actually are limited to one less byte than this,
19 * because the length must include a trailing zero byte.
21 * Changing this requires an initdb.
23 #define NAMEDATALEN 64
26 * Maximum number of arguments to a function.
28 * The minimum value is 8 (GIN indexes use 8-argument support functions).
29 * The maximum possible value is around 600 (limited by index tuple size in
30 * pg_proc's index; BLCKSZ larger than 8K would allow more). Values larger
31 * than needed will waste memory and processing time, but do not directly
34 * Changing this does not require an initdb, but it does require a full
35 * backend recompile (including any user-defined C functions).
37 #define FUNC_MAX_ARGS 100
40 * Maximum number of columns in an index. There is little point in making
41 * this anything but a multiple of 32, because the main cost is associated
42 * with index tuple header size (see access/itup.h).
44 * Changing this requires an initdb.
46 #define INDEX_MAX_KEYS 32
49 * Maximum number of columns in a partition key
51 #define PARTITION_MAX_KEYS 32
54 * When we don't have native spinlocks, we use semaphores to simulate them.
55 * Decreasing this value reduces consumption of OS resources; increasing it
56 * may improve performance, but supplying a real spinlock implementation is
57 * probably far better.
59 #define NUM_SPINLOCK_SEMAPHORES 128
62 * When we have neither spinlocks nor atomic operations support we're
63 * implementing atomic operations on top of spinlock on top of semaphores. To
64 * be safe against atomic operations while holding a spinlock separate
65 * semaphores have to be used.
67 #define NUM_ATOMICS_SEMAPHORES 64
70 * Define this if you want to allow the lo_import and lo_export SQL
71 * functions to be executed by ordinary users. By default these
72 * functions are only available to the Postgres superuser. CAUTION:
73 * These functions are SECURITY HOLES since they can read and write
74 * any file that the PostgreSQL server has permission to access. If
75 * you turn this on, don't say we didn't warn you.
77 /* #define ALLOW_DANGEROUS_LO_FUNCTIONS */
80 * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
81 * maximum usable pathname length is one less).
83 * We'd use a standard system header symbol for this, if there weren't
84 * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
85 * defined by different "standards", and often have different values
86 * on the same platform! So we just punt and use a reasonably
87 * generous setting here.
89 #define MAXPGPATH 1024
92 * PG_SOMAXCONN: maximum accept-queue length limit passed to
93 * listen(2). You'd think we should use SOMAXCONN from
94 * <sys/socket.h>, but on many systems that symbol is much smaller
95 * than the kernel's actual limit. In any case, this symbol need be
96 * twiddled only if you have a kernel that refuses large limit values,
97 * rather than silently reducing the value to what it can handle
98 * (which is what most if not all Unixen do).
100 #define PG_SOMAXCONN 10000
103 * You can try changing this if you have a machine with bytes of
104 * another size, but no guarantee...
106 #define BITS_PER_BYTE 8
109 * Preferred alignment for disk I/O buffers. On some CPUs, copies between
110 * user space and kernel space are significantly faster if the user buffer
111 * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
112 * a platform-dependent value, but for now we just hard-wire it.
114 #define ALIGNOF_BUFFER 32
117 * Disable UNIX sockets for certain operating systems.
120 #undef HAVE_UNIX_SOCKETS
124 * Define this if your operating system supports link()
126 #if !defined(WIN32) && !defined(__CYGWIN__)
127 #define HAVE_WORKING_LINK 1
131 * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
132 * posix_fadvise() kernel call. Usually the automatic configure tests are
133 * sufficient, but some older Linux distributions had broken versions of
134 * posix_fadvise(). If necessary you can remove the #define here.
136 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
137 #define USE_POSIX_FADVISE
141 * USE_PREFETCH code should be compiled only if we have a way to implement
142 * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
143 * might in future be support for alternative low-level prefetch APIs.)
145 #ifdef USE_POSIX_FADVISE
150 * Default and maximum values for backend_flush_after, bgwriter_flush_after
151 * and checkpoint_flush_after; measured in blocks. Currently, these are
152 * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
153 * we could also enable by default if we have mmap and msync(MS_ASYNC)?
155 #ifdef HAVE_SYNC_FILE_RANGE
156 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
157 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
158 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
160 #define DEFAULT_BACKEND_FLUSH_AFTER 0
161 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
162 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
164 /* upper limit for all three variables */
165 #define WRITEBACK_MAX_PENDING_FLUSHES 256
168 * USE_SSL code should be compiled only when compiling with an SSL
169 * implementation. (Currently, only OpenSSL is supported, but we might add
170 * more implementations in the future.)
177 * This is the default directory in which AF_UNIX socket files are
178 * placed. Caution: changing this risks breaking your existing client
179 * applications, which are likely to continue to look in the old
180 * directory. But if you just hate the idea of sockets in /tmp,
181 * here's where to twiddle it. You can also override this at runtime
182 * with the postmaster's -k switch.
184 #define DEFAULT_PGSOCKET_DIR "/tmp"
187 * This is the default event source for Windows event log.
189 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
192 * The random() function is expected to yield values between 0 and
193 * MAX_RANDOM_VALUE. Currently, all known implementations yield
194 * 0..2^31-1, so we just hardwire this constant. We could do a
195 * configure test if it proves to be necessary. CAUTION: Think not to
196 * replace this with RAND_MAX. RAND_MAX defines the maximum value of
197 * the older rand() function, which is often different from --- and
198 * considerably inferior to --- random().
200 #define MAX_RANDOM_VALUE PG_INT32_MAX
203 * On PPC machines, decide whether to use the mutex hint bit in LWARX
204 * instructions. Setting the hint bit will slightly improve spinlock
205 * performance on POWER6 and later machines, but does nothing before that,
206 * and will result in illegal-instruction failures on some pre-POWER4
207 * machines. By default we use the hint bit when building for 64-bit PPC,
208 * which should be safe in nearly all cases. You might want to override
209 * this if you are building 32-bit code for a known-recent PPC machine.
211 #ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
212 #if defined(__ppc64__) || defined(__powerpc64__)
213 #define USE_PPC_LWARX_MUTEX_HINT
218 * On PPC machines, decide whether to use LWSYNC instructions in place of
219 * ISYNC and SYNC. This provides slightly better performance, but will
220 * result in illegal-instruction failures on some pre-POWER4 machines.
221 * By default we use LWSYNC when building for 64-bit PPC, which should be
222 * safe in nearly all cases.
224 #if defined(__ppc64__) || defined(__powerpc64__)
225 #define USE_PPC_LWSYNC
229 * Assumed cache line size. This doesn't affect correctness, but can be used
230 * for low-level optimizations. Currently, this is used to pad some data
231 * structures in xlog.c, to ensure that highly-contended fields are on
232 * different cache lines. Too small a value can hurt performance due to false
233 * sharing, while the only downside of too large a value is a few bytes of
234 * wasted memory. The default is 128, which should be large enough for all
235 * supported platforms.
237 #define PG_CACHE_LINE_SIZE 128
240 *------------------------------------------------------------------------
241 * The following symbols are for enabling debugging code, not for
242 * controlling user-visible features or resource limits.
243 *------------------------------------------------------------------------
247 * Include Valgrind "client requests", mostly in the memory allocator, so
248 * Valgrind understands PostgreSQL memory contexts. This permits detecting
249 * memory errors that Valgrind would not detect on a vanilla build. See also
250 * src/tools/valgrind.supp. "make installcheck" runs 20-30x longer under
251 * Valgrind. Note that USE_VALGRIND slowed older versions of Valgrind by an
252 * additional order of magnitude; Valgrind 3.8.1 does not have this problem.
253 * The client requests fall in hot code paths, so USE_VALGRIND also slows
254 * native execution by a few percentage points.
256 * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
257 * instrumentation of repalloc() is inferior without it.
259 /* #define USE_VALGRIND */
262 * Define this to cause pfree()'d memory to be cleared immediately, to
263 * facilitate catching bugs that refer to already-freed values.
264 * Right now, this gets defined automatically if --enable-cassert.
266 #ifdef USE_ASSERT_CHECKING
267 #define CLOBBER_FREED_MEMORY
271 * Define this to check memory allocation errors (scribbling on more
272 * bytes than were allocated). Right now, this gets defined
273 * automatically if --enable-cassert or USE_VALGRIND.
275 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
276 #define MEMORY_CONTEXT_CHECKING
280 * Define this to cause palloc()'d memory to be filled with random data, to
281 * facilitate catching code that depends on the contents of uninitialized
282 * memory. Caution: this is horrendously expensive.
284 /* #define RANDOMIZE_ALLOCATED_MEMORY */
287 * Define this to force all parse and plan trees to be passed through
288 * copyObject(), to facilitate catching errors and omissions in
291 /* #define COPY_PARSE_PLAN_TREES */
294 * Define this to force all raw parse trees for DML statements to be scanned
295 * by raw_expression_tree_walker(), to facilitate catching errors and
296 * omissions in that function.
298 /* #define RAW_EXPRESSION_COVERAGE_TEST */
301 * Enable debugging print statements for lock-related operations.
303 /* #define LOCK_DEBUG */
306 * Enable debugging print statements for WAL-related operations; see
307 * also the wal_debug GUC var.
309 /* #define WAL_DEBUG */
312 * Enable tracing of resource consumption during sort operations;
313 * see also the trace_sort GUC var. For 8.1 this is enabled by default.
318 * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
320 /* #define TRACE_SYNCSCAN */
323 * Other debug #defines (documentation, anyone?)
325 /* #define HEAPDEBUGALL */
326 /* #define ACLDEBUG */