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pg_config_manual.h
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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 */