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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) 1996-2021, 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 fewer 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  * Decide whether built-in 8-byte types, including float8, int8, and
61  * timestamp, are passed by value. This is on by default if sizeof(Datum) >=
62  * 8 (that is, on 64-bit platforms). If sizeof(Datum) < 8 (32-bit platforms),
63  * this must be off. We keep this here as an option so that it is easy to
64  * test the pass-by-reference code paths on 64-bit platforms.
65  *
66  * Changing this requires an initdb.
67  */
68 #if SIZEOF_VOID_P >= 8
69 #define USE_FLOAT8_BYVAL 1
70 #endif
71 
72 /*
73  * When we don't have native spinlocks, we use semaphores to simulate them.
74  * Decreasing this value reduces consumption of OS resources; increasing it
75  * may improve performance, but supplying a real spinlock implementation is
76  * probably far better.
77  */
78 #define NUM_SPINLOCK_SEMAPHORES 128
79 
80 /*
81  * When we have neither spinlocks nor atomic operations support we're
82  * implementing atomic operations on top of spinlock on top of semaphores. To
83  * be safe against atomic operations while holding a spinlock separate
84  * semaphores have to be used.
85  */
86 #define NUM_ATOMICS_SEMAPHORES 64
87 
88 /*
89  * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
90  * maximum usable pathname length is one less).
91  *
92  * We'd use a standard system header symbol for this, if there weren't
93  * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
94  * defined by different "standards", and often have different values
95  * on the same platform! So we just punt and use a reasonably
96  * generous setting here.
97  */
98 #define MAXPGPATH 1024
99 
100 /*
101  * PG_SOMAXCONN: maximum accept-queue length limit passed to
102  * listen(2). You'd think we should use SOMAXCONN from
103  * <sys/socket.h>, but on many systems that symbol is much smaller
104  * than the kernel's actual limit. In any case, this symbol need be
105  * twiddled only if you have a kernel that refuses large limit values,
106  * rather than silently reducing the value to what it can handle
107  * (which is what most if not all Unixen do).
108  */
109 #define PG_SOMAXCONN 10000
110 
111 /*
112  * You can try changing this if you have a machine with bytes of
113  * another size, but no guarantee...
114  */
115 #define BITS_PER_BYTE 8
116 
117 /*
118  * Preferred alignment for disk I/O buffers. On some CPUs, copies between
119  * user space and kernel space are significantly faster if the user buffer
120  * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
121  * a platform-dependent value, but for now we just hard-wire it.
122  */
123 #define ALIGNOF_BUFFER 32
124 
125 /*
126  * If EXEC_BACKEND is defined, the postmaster uses an alternative method for
127  * starting subprocesses: Instead of simply using fork(), as is standard on
128  * Unix platforms, it uses fork()+exec() or something equivalent on Windows,
129  * as well as lots of extra code to bring the required global state to those
130  * new processes. This must be enabled on Windows (because there is no
131  * fork()). On other platforms, it's only useful for verifying those
132  * otherwise Windows-specific code paths.
133  */
134 #if defined(WIN32) && !defined(__CYGWIN__)
135 #define EXEC_BACKEND
136 #endif
137 
138 /*
139  * Define this if your operating system supports link()
140  */
141 #if !defined(WIN32) && !defined(__CYGWIN__)
142 #define HAVE_WORKING_LINK 1
143 #endif
144 
145 /*
146  * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
147  * posix_fadvise() kernel call. Usually the automatic configure tests are
148  * sufficient, but some older Linux distributions had broken versions of
149  * posix_fadvise(). If necessary you can remove the #define here.
150  */
151 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
152 #define USE_POSIX_FADVISE
153 #endif
154 
155 /*
156  * USE_PREFETCH code should be compiled only if we have a way to implement
157  * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
158  * might in future be support for alternative low-level prefetch APIs.
159  * If you change this, you probably need to adjust the error message in
160  * check_effective_io_concurrency.)
161  */
162 #ifdef USE_POSIX_FADVISE
163 #define USE_PREFETCH
164 #endif
165 
166 /*
167  * Default and maximum values for backend_flush_after, bgwriter_flush_after
168  * and checkpoint_flush_after; measured in blocks. Currently, these are
169  * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
170  * we could also enable by default if we have mmap and msync(MS_ASYNC)?
171  */
172 #ifdef HAVE_SYNC_FILE_RANGE
173 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
174 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
175 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
176 #else
177 #define DEFAULT_BACKEND_FLUSH_AFTER 0
178 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
179 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
180 #endif
181 /* upper limit for all three variables */
182 #define WRITEBACK_MAX_PENDING_FLUSHES 256
183 
184 /*
185  * USE_SSL code should be compiled only when compiling with an SSL
186  * implementation.
187  */
188 #ifdef USE_OPENSSL
189 #define USE_SSL
190 #endif
191 
192 /*
193  * This is the default directory in which AF_UNIX socket files are
194  * placed. Caution: changing this risks breaking your existing client
195  * applications, which are likely to continue to look in the old
196  * directory. But if you just hate the idea of sockets in /tmp,
197  * here's where to twiddle it. You can also override this at runtime
198  * with the postmaster's -k switch.
199  *
200  * If set to an empty string, then AF_UNIX sockets are not used by default: A
201  * server will not create an AF_UNIX socket unless the run-time configuration
202  * is changed, a client will connect via TCP/IP by default and will only use
203  * an AF_UNIX socket if one is explicitly specified.
204  *
205  * This is done by default on Windows because there is no good standard
206  * location for AF_UNIX sockets and many installations on Windows don't
207  * support them yet.
208  */
209 #ifndef WIN32
210 #define DEFAULT_PGSOCKET_DIR "/tmp"
211 #else
212 #define DEFAULT_PGSOCKET_DIR ""
213 #endif
214 
215 /*
216  * This is the default event source for Windows event log.
217  */
218 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
219 
220 /*
221  * The random() function is expected to yield values between 0 and
222  * MAX_RANDOM_VALUE. Currently, all known implementations yield
223  * 0..2^31-1, so we just hardwire this constant. We could do a
224  * configure test if it proves to be necessary. CAUTION: Think not to
225  * replace this with RAND_MAX. RAND_MAX defines the maximum value of
226  * the older rand() function, which is often different from --- and
227  * considerably inferior to --- random().
228  */
229 #define MAX_RANDOM_VALUE PG_INT32_MAX
230 
231 /*
232  * On PPC machines, decide whether to use the mutex hint bit in LWARX
233  * instructions. Setting the hint bit will slightly improve spinlock
234  * performance on POWER6 and later machines, but does nothing before that,
235  * and will result in illegal-instruction failures on some pre-POWER4
236  * machines. By default we use the hint bit when building for 64-bit PPC,
237  * which should be safe in nearly all cases. You might want to override
238  * this if you are building 32-bit code for a known-recent PPC machine.
239  */
240 #ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
241 #if defined(__ppc64__) || defined(__powerpc64__)
242 #define USE_PPC_LWARX_MUTEX_HINT
243 #endif
244 #endif
245 
246 /*
247  * On PPC machines, decide whether to use LWSYNC instructions in place of
248  * ISYNC and SYNC. This provides slightly better performance, but will
249  * result in illegal-instruction failures on some pre-POWER4 machines.
250  * By default we use LWSYNC when building for 64-bit PPC, which should be
251  * safe in nearly all cases.
252  */
253 #if defined(__ppc64__) || defined(__powerpc64__)
254 #define USE_PPC_LWSYNC
255 #endif
256 
257 /*
258  * Assumed cache line size. This doesn't affect correctness, but can be used
259  * for low-level optimizations. Currently, this is used to pad some data
260  * structures in xlog.c, to ensure that highly-contended fields are on
261  * different cache lines. Too small a value can hurt performance due to false
262  * sharing, while the only downside of too large a value is a few bytes of
263  * wasted memory. The default is 128, which should be large enough for all
264  * supported platforms.
265  */
266 #define PG_CACHE_LINE_SIZE 128
267 
268 /*
269  *------------------------------------------------------------------------
270  * The following symbols are for enabling debugging code, not for
271  * controlling user-visible features or resource limits.
272  *------------------------------------------------------------------------
273  */
274 
275 /*
276  * Include Valgrind "client requests", mostly in the memory allocator, so
277  * Valgrind understands PostgreSQL memory contexts. This permits detecting
278  * memory errors that Valgrind would not detect on a vanilla build. It also
279  * enables detection of buffer accesses that take place without holding a
280  * buffer pin (or without holding a buffer lock in the case of index access
281  * methods that superimpose their own custom client requests on top of the
282  * generic bufmgr.c requests). See also src/tools/valgrind.supp.
283  *
284  * "make installcheck" is significantly slower under Valgrind. The client
285  * requests fall in hot code paths, so USE_VALGRIND slows execution by a few
286  * percentage points even when not run under Valgrind.
287  *
288  * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
289  * instrumentation of repalloc() is inferior without it.
290  */
291 /* #define USE_VALGRIND */
292 
293 /*
294  * Define this to cause pfree()'d memory to be cleared immediately, to
295  * facilitate catching bugs that refer to already-freed values.
296  * Right now, this gets defined automatically if --enable-cassert.
297  */
298 #ifdef USE_ASSERT_CHECKING
299 #define CLOBBER_FREED_MEMORY
300 #endif
301 
302 /*
303  * Define this to check memory allocation errors (scribbling on more
304  * bytes than were allocated). Right now, this gets defined
305  * automatically if --enable-cassert or USE_VALGRIND.
306  */
307 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
308 #define MEMORY_CONTEXT_CHECKING
309 #endif
310 
311 /*
312  * Define this to cause palloc()'d memory to be filled with random data, to
313  * facilitate catching code that depends on the contents of uninitialized
314  * memory. Caution: this is horrendously expensive.
315  */
316 /* #define RANDOMIZE_ALLOCATED_MEMORY */
317 
318 /*
319  * For cache invalidation debugging, define CLOBBER_CACHE_ENABLED to enable
320  * use of the debug_invalidate_system_caches_always GUC to aggressively flush
321  * syscache/relcache entries whenever it's possible to deliver invalidations.
322  * See AcceptInvalidationMessages() in src/backend/utils/cache/inval.c for
323  * details.
324  *
325  * USE_ASSERT_CHECKING builds default to enabling this. It's possible to use
326  * CLOBBER_CACHE_ENABLED without a cassert build and the implied
327  * CLOBBER_FREED_MEMORY and MEMORY_CONTEXT_CHECKING options but it's unlikely
328  * to be as effective at identifying problems.
329  */
330 /* #define CLOBBER_CACHE_ENABLED */
331 
332 #if defined(USE_ASSERT_CHECKING) && !defined(CLOBBER_CACHE_ENABLED)
333 #define CLOBBER_CACHE_ENABLED
334 #endif
335 
336 /*
337  * Backwards compatibility for the older compile-time-only cache clobber
338  * macros.
339  */
340 #if !defined(CLOBBER_CACHE_ENABLED) && (defined(CLOBBER_CACHE_ALWAYS) || defined(CLOBBER_CACHE_RECURSIVELY))
341 #define CLOBBER_CACHE_ENABLED
342 #endif
343 
344 /*
345  * Recover memory used for relcache entries when invalidated. See
346  * RelationBuildDescr() in src/backend/utils/cache/relcache.c.
347  *
348  * This is active automatically for clobber cache builds when clobbering is
349  * active, but can be overridden here by explicitly defining
350  * RECOVER_RELATION_BUILD_MEMORY. Define to 1 to always free relation cache
351  * memory even when clobber is off, or to 0 to never free relation cache
352  * memory even when clobbering is on.
353  */
354 /* #define RECOVER_RELATION_BUILD_MEMORY 0 */ /* Force disable */
355 /* #define RECOVER_RELATION_BUILD_MEMORY 1 */ /* Force enable */
356 
357 /*
358  * Define this to force all parse and plan trees to be passed through
359  * copyObject(), to facilitate catching errors and omissions in
360  * copyObject().
361  */
362 /* #define COPY_PARSE_PLAN_TREES */
363 
364 /*
365  * Define this to force all parse and plan trees to be passed through
366  * outfuncs.c/readfuncs.c, to facilitate catching errors and omissions in
367  * those modules.
368  */
369 /* #define WRITE_READ_PARSE_PLAN_TREES */
370 
371 /*
372  * Define this to force all raw parse trees for DML statements to be scanned
373  * by raw_expression_tree_walker(), to facilitate catching errors and
374  * omissions in that function.
375  */
376 /* #define RAW_EXPRESSION_COVERAGE_TEST */
377 
378 /*
379  * Enable debugging print statements for lock-related operations.
380  */
381 /* #define LOCK_DEBUG */
382 
383 /*
384  * Enable debugging print statements for WAL-related operations; see
385  * also the wal_debug GUC var.
386  */
387 /* #define WAL_DEBUG */
388 
389 /*
390  * Enable tracing of resource consumption during sort operations;
391  * see also the trace_sort GUC var. For 8.1 this is enabled by default.
392  */
393 #define TRACE_SORT 1
394 
395 /*
396  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
397  */
398 /* #define TRACE_SYNCSCAN */