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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) 1996-2017, 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 default value for wal_segment_size to be used at initdb when run
18  * without --walsegsize option. 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  * Define this if you want to allow the lo_import and lo_export SQL
77  * functions to be executed by ordinary users. By default these
78  * functions are only available to the Postgres superuser. CAUTION:
79  * These functions are SECURITY HOLES since they can read and write
80  * any file that the PostgreSQL server has permission to access. If
81  * you turn this on, don't say we didn't warn you.
82  */
83 /* #define ALLOW_DANGEROUS_LO_FUNCTIONS */
84 
85 /*
86  * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
87  * maximum usable pathname length is one less).
88  *
89  * We'd use a standard system header symbol for this, if there weren't
90  * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
91  * defined by different "standards", and often have different values
92  * on the same platform! So we just punt and use a reasonably
93  * generous setting here.
94  */
95 #define MAXPGPATH 1024
96 
97 /*
98  * PG_SOMAXCONN: maximum accept-queue length limit passed to
99  * listen(2). You'd think we should use SOMAXCONN from
100  * <sys/socket.h>, but on many systems that symbol is much smaller
101  * than the kernel's actual limit. In any case, this symbol need be
102  * twiddled only if you have a kernel that refuses large limit values,
103  * rather than silently reducing the value to what it can handle
104  * (which is what most if not all Unixen do).
105  */
106 #define PG_SOMAXCONN 10000
107 
108 /*
109  * You can try changing this if you have a machine with bytes of
110  * another size, but no guarantee...
111  */
112 #define BITS_PER_BYTE 8
113 
114 /*
115  * Preferred alignment for disk I/O buffers. On some CPUs, copies between
116  * user space and kernel space are significantly faster if the user buffer
117  * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
118  * a platform-dependent value, but for now we just hard-wire it.
119  */
120 #define ALIGNOF_BUFFER 32
121 
122 /*
123  * Disable UNIX sockets for certain operating systems.
124  */
125 #if defined(WIN32)
126 #undef HAVE_UNIX_SOCKETS
127 #endif
128 
129 /*
130  * Define this if your operating system supports link()
131  */
132 #if !defined(WIN32) && !defined(__CYGWIN__)
133 #define HAVE_WORKING_LINK 1
134 #endif
135 
136 /*
137  * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
138  * posix_fadvise() kernel call. Usually the automatic configure tests are
139  * sufficient, but some older Linux distributions had broken versions of
140  * posix_fadvise(). If necessary you can remove the #define here.
141  */
142 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
143 #define USE_POSIX_FADVISE
144 #endif
145 
146 /*
147  * USE_PREFETCH code should be compiled only if we have a way to implement
148  * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
149  * might in future be support for alternative low-level prefetch APIs.)
150  */
151 #ifdef USE_POSIX_FADVISE
152 #define USE_PREFETCH
153 #endif
154 
155 /*
156  * Default and maximum values for backend_flush_after, bgwriter_flush_after
157  * and checkpoint_flush_after; measured in blocks. Currently, these are
158  * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
159  * we could also enable by default if we have mmap and msync(MS_ASYNC)?
160  */
161 #ifdef HAVE_SYNC_FILE_RANGE
162 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
163 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
164 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
165 #else
166 #define DEFAULT_BACKEND_FLUSH_AFTER 0
167 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
168 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
169 #endif
170 /* upper limit for all three variables */
171 #define WRITEBACK_MAX_PENDING_FLUSHES 256
172 
173 /*
174  * USE_SSL code should be compiled only when compiling with an SSL
175  * implementation. (Currently, only OpenSSL is supported, but we might add
176  * more implementations in the future.)
177  */
178 #ifdef USE_OPENSSL
179 #define USE_SSL
180 #endif
181 
182 /*
183  * This is the default directory in which AF_UNIX socket files are
184  * placed. Caution: changing this risks breaking your existing client
185  * applications, which are likely to continue to look in the old
186  * directory. But if you just hate the idea of sockets in /tmp,
187  * here's where to twiddle it. You can also override this at runtime
188  * with the postmaster's -k switch.
189  */
190 #define DEFAULT_PGSOCKET_DIR "/tmp"
191 
192 /*
193  * This is the default event source for Windows event log.
194  */
195 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
196 
197 /*
198  * The random() function is expected to yield values between 0 and
199  * MAX_RANDOM_VALUE. Currently, all known implementations yield
200  * 0..2^31-1, so we just hardwire this constant. We could do a
201  * configure test if it proves to be necessary. CAUTION: Think not to
202  * replace this with RAND_MAX. RAND_MAX defines the maximum value of
203  * the older rand() function, which is often different from --- and
204  * considerably inferior to --- random().
205  */
206 #define MAX_RANDOM_VALUE PG_INT32_MAX
207 
208 /*
209  * On PPC machines, decide whether to use the mutex hint bit in LWARX
210  * instructions. Setting the hint bit will slightly improve spinlock
211  * performance on POWER6 and later machines, but does nothing before that,
212  * and will result in illegal-instruction failures on some pre-POWER4
213  * machines. By default we use the hint bit when building for 64-bit PPC,
214  * which should be safe in nearly all cases. You might want to override
215  * this if you are building 32-bit code for a known-recent PPC machine.
216  */
217 #ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
218 #if defined(__ppc64__) || defined(__powerpc64__)
219 #define USE_PPC_LWARX_MUTEX_HINT
220 #endif
221 #endif
222 
223 /*
224  * On PPC machines, decide whether to use LWSYNC instructions in place of
225  * ISYNC and SYNC. This provides slightly better performance, but will
226  * result in illegal-instruction failures on some pre-POWER4 machines.
227  * By default we use LWSYNC when building for 64-bit PPC, which should be
228  * safe in nearly all cases.
229  */
230 #if defined(__ppc64__) || defined(__powerpc64__)
231 #define USE_PPC_LWSYNC
232 #endif
233 
234 /*
235  * Assumed cache line size. This doesn't affect correctness, but can be used
236  * for low-level optimizations. Currently, this is used to pad some data
237  * structures in xlog.c, to ensure that highly-contended fields are on
238  * different cache lines. Too small a value can hurt performance due to false
239  * sharing, while the only downside of too large a value is a few bytes of
240  * wasted memory. The default is 128, which should be large enough for all
241  * supported platforms.
242  */
243 #define PG_CACHE_LINE_SIZE 128
244 
245 /*
246  *------------------------------------------------------------------------
247  * The following symbols are for enabling debugging code, not for
248  * controlling user-visible features or resource limits.
249  *------------------------------------------------------------------------
250  */
251 
252 /*
253  * Include Valgrind "client requests", mostly in the memory allocator, so
254  * Valgrind understands PostgreSQL memory contexts. This permits detecting
255  * memory errors that Valgrind would not detect on a vanilla build. See also
256  * src/tools/valgrind.supp. "make installcheck" runs 20-30x longer under
257  * Valgrind. Note that USE_VALGRIND slowed older versions of Valgrind by an
258  * additional order of magnitude; Valgrind 3.8.1 does not have this problem.
259  * The client requests fall in hot code paths, so USE_VALGRIND also slows
260  * native execution by a few percentage points.
261  *
262  * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
263  * instrumentation of repalloc() is inferior without it.
264  */
265 /* #define USE_VALGRIND */
266 
267 /*
268  * Define this to cause pfree()'d memory to be cleared immediately, to
269  * facilitate catching bugs that refer to already-freed values.
270  * Right now, this gets defined automatically if --enable-cassert.
271  */
272 #ifdef USE_ASSERT_CHECKING
273 #define CLOBBER_FREED_MEMORY
274 #endif
275 
276 /*
277  * Define this to check memory allocation errors (scribbling on more
278  * bytes than were allocated). Right now, this gets defined
279  * automatically if --enable-cassert or USE_VALGRIND.
280  */
281 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
282 #define MEMORY_CONTEXT_CHECKING
283 #endif
284 
285 /*
286  * Define this to cause palloc()'d memory to be filled with random data, to
287  * facilitate catching code that depends on the contents of uninitialized
288  * memory. Caution: this is horrendously expensive.
289  */
290 /* #define RANDOMIZE_ALLOCATED_MEMORY */
291 
292 /*
293  * Define this to force all parse and plan trees to be passed through
294  * copyObject(), to facilitate catching errors and omissions in
295  * copyObject().
296  */
297 /* #define COPY_PARSE_PLAN_TREES */
298 
299 /*
300  * Define this to force all raw parse trees for DML statements to be scanned
301  * by raw_expression_tree_walker(), to facilitate catching errors and
302  * omissions in that function.
303  */
304 /* #define RAW_EXPRESSION_COVERAGE_TEST */
305 
306 /*
307  * Enable debugging print statements for lock-related operations.
308  */
309 /* #define LOCK_DEBUG */
310 
311 /*
312  * Enable debugging print statements for WAL-related operations; see
313  * also the wal_debug GUC var.
314  */
315 /* #define WAL_DEBUG */
316 
317 /*
318  * Enable tracing of resource consumption during sort operations;
319  * see also the trace_sort GUC var. For 8.1 this is enabled by default.
320  */
321 #define TRACE_SORT 1
322 
323 /*
324  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
325  */
326 /* #define TRACE_SYNCSCAN */
327 
328 /*
329  * Other debug #defines (documentation, anyone?)
330  */
331 /* #define HEAPDEBUGALL */
332 /* #define ACLDEBUG */