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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  * 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.
20  *
21  * Changing this requires an initdb.
22  */
23 #define NAMEDATALEN 64
24 
25 /*
26  * Maximum number of arguments to a function.
27  *
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
32  * cost disk space.
33  *
34  * Changing this does not require an initdb, but it does require a full
35  * backend recompile (including any user-defined C functions).
36  */
37 #define FUNC_MAX_ARGS 100
38 
39 /*
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).
43  *
44  * Changing this requires an initdb.
45  */
46 #define INDEX_MAX_KEYS 32
47 
48 /*
49  * Maximum number of columns in a partition key
50  */
51 #define PARTITION_MAX_KEYS 32
52 
53 /*
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.
58  */
59 #define NUM_SPINLOCK_SEMAPHORES 128
60 
61 /*
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.
66  */
67 #define NUM_ATOMICS_SEMAPHORES 64
68 
69 /*
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.
76  */
77 /* #define ALLOW_DANGEROUS_LO_FUNCTIONS */
78 
79 /*
80  * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
81  * maximum usable pathname length is one less).
82  *
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.
88  */
89 #define MAXPGPATH 1024
90 
91 /*
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).
99  */
100 #define PG_SOMAXCONN 10000
101 
102 /*
103  * You can try changing this if you have a machine with bytes of
104  * another size, but no guarantee...
105  */
106 #define BITS_PER_BYTE 8
107 
108 /*
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.
113  */
114 #define ALIGNOF_BUFFER 32
115 
116 /*
117  * Disable UNIX sockets for certain operating systems.
118  */
119 #if defined(WIN32)
120 #undef HAVE_UNIX_SOCKETS
121 #endif
122 
123 /*
124  * Define this if your operating system supports link()
125  */
126 #if !defined(WIN32) && !defined(__CYGWIN__)
127 #define HAVE_WORKING_LINK 1
128 #endif
129 
130 /*
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.
135  */
136 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
137 #define USE_POSIX_FADVISE
138 #endif
139 
140 /*
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.)
144  */
145 #ifdef USE_POSIX_FADVISE
146 #define USE_PREFETCH
147 #endif
148 
149 /*
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)?
154  */
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
159 #else
160 #define DEFAULT_BACKEND_FLUSH_AFTER 0
161 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
162 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
163 #endif
164 /* upper limit for all three variables */
165 #define WRITEBACK_MAX_PENDING_FLUSHES 256
166 
167 /*
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.)
171  */
172 #ifdef USE_OPENSSL
173 #define USE_SSL
174 #endif
175 
176 /*
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.
183  */
184 #define DEFAULT_PGSOCKET_DIR "/tmp"
185 
186 /*
187  * This is the default event source for Windows event log.
188  */
189 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
190 
191 /*
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().
199  */
200 #define MAX_RANDOM_VALUE PG_INT32_MAX
201 
202 /*
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.
210  */
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
214 #endif
215 #endif
216 
217 /*
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.
223  */
224 #if defined(__ppc64__) || defined(__powerpc64__)
225 #define USE_PPC_LWSYNC
226 #endif
227 
228 /*
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.
236  */
237 #define PG_CACHE_LINE_SIZE 128
238 
239 /*
240  *------------------------------------------------------------------------
241  * The following symbols are for enabling debugging code, not for
242  * controlling user-visible features or resource limits.
243  *------------------------------------------------------------------------
244  */
245 
246 /*
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.
255  *
256  * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
257  * instrumentation of repalloc() is inferior without it.
258  */
259 /* #define USE_VALGRIND */
260 
261 /*
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.
265  */
266 #ifdef USE_ASSERT_CHECKING
267 #define CLOBBER_FREED_MEMORY
268 #endif
269 
270 /*
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.
274  */
275 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
276 #define MEMORY_CONTEXT_CHECKING
277 #endif
278 
279 /*
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.
283  */
284 /* #define RANDOMIZE_ALLOCATED_MEMORY */
285 
286 /*
287  * Define this to force all parse and plan trees to be passed through
288  * copyObject(), to facilitate catching errors and omissions in
289  * copyObject().
290  */
291 /* #define COPY_PARSE_PLAN_TREES */
292 
293 /*
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.
297  */
298 /* #define RAW_EXPRESSION_COVERAGE_TEST */
299 
300 /*
301  * Enable debugging print statements for lock-related operations.
302  */
303 /* #define LOCK_DEBUG */
304 
305 /*
306  * Enable debugging print statements for WAL-related operations; see
307  * also the wal_debug GUC var.
308  */
309 /* #define WAL_DEBUG */
310 
311 /*
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.
314  */
315 #define TRACE_SORT 1
316 
317 /*
318  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
319  */
320 /* #define TRACE_SYNCSCAN */
321 
322 /*
323  * Other debug #defines (documentation, anyone?)
324  */
325 /* #define HEAPDEBUGALL */
326 /* #define ACLDEBUG */