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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  * 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  */
141 #ifdef USE_POSIX_FADVISE
142 #define USE_PREFETCH
143 #endif
144 
145 /*
146  * Default and maximum values for backend_flush_after, bgwriter_flush_after
147  * and checkpoint_flush_after; measured in blocks. Currently, these are
148  * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
149  * we could also enable by default if we have mmap and msync(MS_ASYNC)?
150  */
151 #ifdef HAVE_SYNC_FILE_RANGE
152 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
153 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
154 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
155 #else
156 #define DEFAULT_BACKEND_FLUSH_AFTER 0
157 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
158 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
159 #endif
160 /* upper limit for all three variables */
161 #define WRITEBACK_MAX_PENDING_FLUSHES 256
162 
163 /*
164  * USE_SSL code should be compiled only when compiling with an SSL
165  * implementation. (Currently, only OpenSSL is supported, but we might add
166  * more implementations in the future.)
167  */
168 #ifdef USE_OPENSSL
169 #define USE_SSL
170 #endif
171 
172 /*
173  * This is the default directory in which AF_UNIX socket files are
174  * placed. Caution: changing this risks breaking your existing client
175  * applications, which are likely to continue to look in the old
176  * directory. But if you just hate the idea of sockets in /tmp,
177  * here's where to twiddle it. You can also override this at runtime
178  * with the postmaster's -k switch.
179  */
180 #define DEFAULT_PGSOCKET_DIR "/tmp"
181 
182 /*
183  * This is the default event source for Windows event log.
184  */
185 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
186 
187 /*
188  * The random() function is expected to yield values between 0 and
189  * MAX_RANDOM_VALUE. Currently, all known implementations yield
190  * 0..2^31-1, so we just hardwire this constant. We could do a
191  * configure test if it proves to be necessary. CAUTION: Think not to
192  * replace this with RAND_MAX. RAND_MAX defines the maximum value of
193  * the older rand() function, which is often different from --- and
194  * considerably inferior to --- random().
195  */
196 #define MAX_RANDOM_VALUE PG_INT32_MAX
197 
198 /*
199  * On PPC machines, decide whether to use the mutex hint bit in LWARX
200  * instructions. Setting the hint bit will slightly improve spinlock
201  * performance on POWER6 and later machines, but does nothing before that,
202  * and will result in illegal-instruction failures on some pre-POWER4
203  * machines. By default we use the hint bit when building for 64-bit PPC,
204  * which should be safe in nearly all cases. You might want to override
205  * this if you are building 32-bit code for a known-recent PPC machine.
206  */
207 #ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
208 #if defined(__ppc64__) || defined(__powerpc64__)
209 #define USE_PPC_LWARX_MUTEX_HINT
210 #endif
211 #endif
212 
213 /*
214  * On PPC machines, decide whether to use LWSYNC instructions in place of
215  * ISYNC and SYNC. This provides slightly better performance, but will
216  * result in illegal-instruction failures on some pre-POWER4 machines.
217  * By default we use LWSYNC when building for 64-bit PPC, which should be
218  * safe in nearly all cases.
219  */
220 #if defined(__ppc64__) || defined(__powerpc64__)
221 #define USE_PPC_LWSYNC
222 #endif
223 
224 /*
225  * Assumed cache line size. This doesn't affect correctness, but can be used
226  * for low-level optimizations. Currently, this is used to pad some data
227  * structures in xlog.c, to ensure that highly-contended fields are on
228  * different cache lines. Too small a value can hurt performance due to false
229  * sharing, while the only downside of too large a value is a few bytes of
230  * wasted memory. The default is 128, which should be large enough for all
231  * supported platforms.
232  */
233 #define PG_CACHE_LINE_SIZE 128
234 
235 /*
236  *------------------------------------------------------------------------
237  * The following symbols are for enabling debugging code, not for
238  * controlling user-visible features or resource limits.
239  *------------------------------------------------------------------------
240  */
241 
242 /*
243  * Include Valgrind "client requests", mostly in the memory allocator, so
244  * Valgrind understands PostgreSQL memory contexts. This permits detecting
245  * memory errors that Valgrind would not detect on a vanilla build. See also
246  * src/tools/valgrind.supp. "make installcheck" runs 20-30x longer under
247  * Valgrind. Note that USE_VALGRIND slowed older versions of Valgrind by an
248  * additional order of magnitude; Valgrind 3.8.1 does not have this problem.
249  * The client requests fall in hot code paths, so USE_VALGRIND also slows
250  * native execution by a few percentage points.
251  *
252  * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
253  * instrumentation of repalloc() is inferior without it.
254  */
255 /* #define USE_VALGRIND */
256 
257 /*
258  * Define this to cause pfree()'d memory to be cleared immediately, to
259  * facilitate catching bugs that refer to already-freed values.
260  * Right now, this gets defined automatically if --enable-cassert.
261  */
262 #ifdef USE_ASSERT_CHECKING
263 #define CLOBBER_FREED_MEMORY
264 #endif
265 
266 /*
267  * Define this to check memory allocation errors (scribbling on more
268  * bytes than were allocated). Right now, this gets defined
269  * automatically if --enable-cassert or USE_VALGRIND.
270  */
271 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
272 #define MEMORY_CONTEXT_CHECKING
273 #endif
274 
275 /*
276  * Define this to cause palloc()'d memory to be filled with random data, to
277  * facilitate catching code that depends on the contents of uninitialized
278  * memory. Caution: this is horrendously expensive.
279  */
280 /* #define RANDOMIZE_ALLOCATED_MEMORY */
281 
282 /*
283  * Define this to force all parse and plan trees to be passed through
284  * copyObject(), to facilitate catching errors and omissions in
285  * copyObject().
286  */
287 /* #define COPY_PARSE_PLAN_TREES */
288 
289 /*
290  * Define this to force all raw parse trees for DML statements to be scanned
291  * by raw_expression_tree_walker(), to facilitate catching errors and
292  * omissions in that function.
293  */
294 /* #define RAW_EXPRESSION_COVERAGE_TEST */
295 
296 /*
297  * Enable debugging print statements for lock-related operations.
298  */
299 /* #define LOCK_DEBUG */
300 
301 /*
302  * Enable debugging print statements for WAL-related operations; see
303  * also the wal_debug GUC var.
304  */
305 /* #define WAL_DEBUG */
306 
307 /*
308  * Enable tracing of resource consumption during sort operations;
309  * see also the trace_sort GUC var. For 8.1 this is enabled by default.
310  */
311 #define TRACE_SORT 1
312 
313 /*
314  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
315  */
316 /* #define TRACE_SYNCSCAN */
317 
318 /*
319  * Other debug #defines (documentation, anyone?)
320  */
321 /* #define HEAPDEBUGALL */
322 /* #define ACLDEBUG */