1/*------------------------------------------------------------------------
2 * PostgreSQL manual configuration settings
3 *
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).
8 *
9 * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
10 * Portions Copyright (c) 1994, Regents of the University of California
11 *
12 * src/include/pg_config_manual.h
13 *------------------------------------------------------------------------
14 */
15
16/*
17 * This is the default value for wal_segment_size to be used when initdb is run
18 * without the --wal-segsize option. It must be a valid segment size.
19 */
20#define DEFAULT_XLOG_SEG_SIZE (16*1024*1024)
21
22/*
23 * Maximum length for identifiers (e.g. table names, column names,
24 * function names). Names actually are limited to one less byte than this,
25 * because the length must include a trailing zero byte.
26 *
27 * Changing this requires an initdb.
28 */
29#define NAMEDATALEN 64
30
31/*
32 * Maximum number of arguments to a function.
33 *
34 * The minimum value is 8 (GIN indexes use 8-argument support functions).
35 * The maximum possible value is around 600 (limited by index tuple size in
36 * pg_proc's index; BLCKSZ larger than 8K would allow more). Values larger
37 * than needed will waste memory and processing time, but do not directly
38 * cost disk space.
39 *
40 * Changing this does not require an initdb, but it does require a full
41 * backend recompile (including any user-defined C functions).
42 */
43#define FUNC_MAX_ARGS 100
44
45/*
46 * Maximum number of columns in an index. There is little point in making
47 * this anything but a multiple of 32, because the main cost is associated
48 * with index tuple header size (see access/itup.h).
49 *
50 * Changing this requires an initdb.
51 */
52#define INDEX_MAX_KEYS 32
53
54/*
55 * Maximum number of columns in a partition key
56 */
57#define PARTITION_MAX_KEYS 32
58
59/*
60 * When we don't have native spinlocks, we use semaphores to simulate them.
61 * Decreasing this value reduces consumption of OS resources; increasing it
62 * may improve performance, but supplying a real spinlock implementation is
63 * probably far better.
64 */
65#define NUM_SPINLOCK_SEMAPHORES 128
66
67/*
68 * When we have neither spinlocks nor atomic operations support we're
69 * implementing atomic operations on top of spinlock on top of semaphores. To
70 * be safe against atomic operations while holding a spinlock separate
71 * semaphores have to be used.
72 */
73#define NUM_ATOMICS_SEMAPHORES 64
74
75/*
76 * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
77 * maximum usable pathname length is one less).
78 *
79 * We'd use a standard system header symbol for this, if there weren't
80 * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
81 * defined by different "standards", and often have different values
82 * on the same platform! So we just punt and use a reasonably
83 * generous setting here.
84 */
85#define MAXPGPATH 1024
86
87/*
88 * PG_SOMAXCONN: maximum accept-queue length limit passed to
89 * listen(2). You'd think we should use SOMAXCONN from
90 * <sys/socket.h>, but on many systems that symbol is much smaller
91 * than the kernel's actual limit. In any case, this symbol need be
92 * twiddled only if you have a kernel that refuses large limit values,
93 * rather than silently reducing the value to what it can handle
94 * (which is what most if not all Unixen do).
95 */
96#define PG_SOMAXCONN 10000
97
98/*
99 * You can try changing this if you have a machine with bytes of
100 * another size, but no guarantee...
101 */
102#define BITS_PER_BYTE 8
103
104/*
105 * Preferred alignment for disk I/O buffers. On some CPUs, copies between
106 * user space and kernel space are significantly faster if the user buffer
107 * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
108 * a platform-dependent value, but for now we just hard-wire it.
109 */
110#define ALIGNOF_BUFFER 32
111
112/*
113 * Disable UNIX sockets for certain operating systems.
114 */
115#if defined(WIN32)
116#undef HAVE_UNIX_SOCKETS
117#endif
118
119/*
120 * Define this if your operating system supports link()
121 */
122#if !defined(WIN32) && !defined(__CYGWIN__)
123#define HAVE_WORKING_LINK 1
124#endif
125
126/*
127 * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
128 * posix_fadvise() kernel call. Usually the automatic configure tests are
129 * sufficient, but some older Linux distributions had broken versions of
130 * posix_fadvise(). If necessary you can remove the #define here.
131 */
132#if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
133#define USE_POSIX_FADVISE
134#endif
135
136/*
137 * USE_PREFETCH code should be compiled only if we have a way to implement
138 * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
139 * might in future be support for alternative low-level prefetch APIs.
140 * If you change this, you probably need to adjust the error message in
141 * check_effective_io_concurrency.)
142 */
143#ifdef USE_POSIX_FADVISE
144#define USE_PREFETCH
145#endif
146
147/*
148 * Default and maximum values for backend_flush_after, bgwriter_flush_after
149 * and checkpoint_flush_after; measured in blocks. Currently, these are
150 * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
151 * we could also enable by default if we have mmap and msync(MS_ASYNC)?
152 */
153#ifdef HAVE_SYNC_FILE_RANGE
154#define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
155#define DEFAULT_BGWRITER_FLUSH_AFTER 64
156#define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
157#else
158#define DEFAULT_BACKEND_FLUSH_AFTER 0
159#define DEFAULT_BGWRITER_FLUSH_AFTER 0
160#define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
161#endif
162/* upper limit for all three variables */
163#define WRITEBACK_MAX_PENDING_FLUSHES 256
164
165/*
166 * USE_SSL code should be compiled only when compiling with an SSL
167 * implementation. (Currently, only OpenSSL is supported, but we might add
168 * more implementations in the future.)
169 */
170#ifdef USE_OPENSSL
171#define USE_SSL
172#endif
173
174/*
175 * This is the default directory in which AF_UNIX socket files are
176 * placed. Caution: changing this risks breaking your existing client
177 * applications, which are likely to continue to look in the old
178 * directory. But if you just hate the idea of sockets in /tmp,
179 * here's where to twiddle it. You can also override this at runtime
180 * with the postmaster's -k switch.
181 */
182#define DEFAULT_PGSOCKET_DIR "/tmp"
183
184/*
185 * This is the default event source for Windows event log.
186 */
187#define DEFAULT_EVENT_SOURCE "PostgreSQL"
188
189/*
190 * The random() function is expected to yield values between 0 and
191 * MAX_RANDOM_VALUE. Currently, all known implementations yield
192 * 0..2^31-1, so we just hardwire this constant. We could do a
193 * configure test if it proves to be necessary. CAUTION: Think not to
194 * replace this with RAND_MAX. RAND_MAX defines the maximum value of
195 * the older rand() function, which is often different from --- and
196 * considerably inferior to --- random().
197 */
198#define MAX_RANDOM_VALUE PG_INT32_MAX
199
200/*
201 * On PPC machines, decide whether to use the mutex hint bit in LWARX
202 * instructions. Setting the hint bit will slightly improve spinlock
203 * performance on POWER6 and later machines, but does nothing before that,
204 * and will result in illegal-instruction failures on some pre-POWER4
205 * machines. By default we use the hint bit when building for 64-bit PPC,
206 * which should be safe in nearly all cases. You might want to override
207 * this if you are building 32-bit code for a known-recent PPC machine.
208 */
209#ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
210#if defined(__ppc64__) || defined(__powerpc64__)
211#define USE_PPC_LWARX_MUTEX_HINT
212#endif
213#endif
214
215/*
216 * On PPC machines, decide whether to use LWSYNC instructions in place of
217 * ISYNC and SYNC. This provides slightly better performance, but will
218 * result in illegal-instruction failures on some pre-POWER4 machines.
219 * By default we use LWSYNC when building for 64-bit PPC, which should be
220 * safe in nearly all cases.
221 */
222#if defined(__ppc64__) || defined(__powerpc64__)
223#define USE_PPC_LWSYNC
224#endif
225
226/*
227 * Assumed cache line size. This doesn't affect correctness, but can be used
228 * for low-level optimizations. Currently, this is used to pad some data
229 * structures in xlog.c, to ensure that highly-contended fields are on
230 * different cache lines. Too small a value can hurt performance due to false
231 * sharing, while the only downside of too large a value is a few bytes of
232 * wasted memory. The default is 128, which should be large enough for all
233 * supported platforms.
234 */
235#define PG_CACHE_LINE_SIZE 128
236
237/*
238 *------------------------------------------------------------------------
239 * The following symbols are for enabling debugging code, not for
240 * controlling user-visible features or resource limits.
241 *------------------------------------------------------------------------
242 */
243
244/*
245 * Include Valgrind "client requests", mostly in the memory allocator, so
246 * Valgrind understands PostgreSQL memory contexts. This permits detecting
247 * memory errors that Valgrind would not detect on a vanilla build. See also
248 * src/tools/valgrind.supp. "make installcheck" runs 20-30x longer under
249 * Valgrind. Note that USE_VALGRIND slowed older versions of Valgrind by an
250 * additional order of magnitude; Valgrind 3.8.1 does not have this problem.
251 * The client requests fall in hot code paths, so USE_VALGRIND also slows
252 * native execution by a few percentage points.
253 *
254 * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
255 * instrumentation of repalloc() is inferior without it.
256 */
257/* #define USE_VALGRIND */
258
259/*
260 * Define this to cause pfree()'d memory to be cleared immediately, to
261 * facilitate catching bugs that refer to already-freed values.
262 * Right now, this gets defined automatically if --enable-cassert.
263 */
264#ifdef USE_ASSERT_CHECKING
265#define CLOBBER_FREED_MEMORY
266#endif
267
268/*
269 * Define this to check memory allocation errors (scribbling on more
270 * bytes than were allocated). Right now, this gets defined
271 * automatically if --enable-cassert or USE_VALGRIND.
272 */
273#if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
274#define MEMORY_CONTEXT_CHECKING
275#endif
276
277/*
278 * Define this to cause palloc()'d memory to be filled with random data, to
279 * facilitate catching code that depends on the contents of uninitialized
280 * memory. Caution: this is horrendously expensive.
281 */
282/* #define RANDOMIZE_ALLOCATED_MEMORY */
283
284/*
285 * Define this to force all parse and plan trees to be passed through
286 * copyObject(), to facilitate catching errors and omissions in
287 * copyObject().
288 */
289/* #define COPY_PARSE_PLAN_TREES */
290
291/*
292 * Define this to force all parse and plan trees to be passed through
293 * outfuncs.c/readfuncs.c, to facilitate catching errors and omissions in
294 * those modules.
295 */
296/* #define WRITE_READ_PARSE_PLAN_TREES */
297
298/*
299 * Define this to force all raw parse trees for DML statements to be scanned
300 * by raw_expression_tree_walker(), to facilitate catching errors and
301 * omissions in that function.
302 */
303/* #define RAW_EXPRESSION_COVERAGE_TEST */
304
305/*
306 * Enable debugging print statements for lock-related operations.
307 */
308/* #define LOCK_DEBUG */
309
310/*
311 * Enable debugging print statements for WAL-related operations; see
312 * also the wal_debug GUC var.
313 */
314/* #define WAL_DEBUG */
315
316/*
317 * Enable tracing of resource consumption during sort operations;
318 * see also the trace_sort GUC var. For 8.1 this is enabled by default.
319 */
320#define TRACE_SORT 1
321
322/*
323 * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
324 */
325/* #define TRACE_SYNCSCAN */
326
327/*
328 * Other debug #defines (documentation, anyone?)
329 */
330/* #define HEAPDEBUGALL */
331/* #define ACLDEBUG */
332