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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) 1996-2022, 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  * When creating a product derived from PostgreSQL with changes that cause
47  * incompatibilities for loadable modules, it is recommended to change this
48  * string so that dfmgr.c can refuse to load incompatible modules with a clean
49  * error message. Typical examples that cause incompatibilities are any
50  * changes to node tags or node structures. (Note that dfmgr.c already
51  * detects common sources of incompatibilities due to major version
52  * differences and due to some changed compile-time constants. This setting
53  * is for catching anything that cannot be detected in a straightforward way.)
54  *
55  * There is no prescribed format for the string. The suggestion is to include
56  * product or company name, and optionally any internally-relevant ABI
57  * version. Example: "ACME Postgres/1.2". Note that the string will appear
58  * in a user-facing error message if an ABI mismatch is detected.
59  */
60 #define FMGR_ABI_EXTRA "PostgreSQL"
61 
62 /*
63  * Maximum number of columns in an index. There is little point in making
64  * this anything but a multiple of 32, because the main cost is associated
65  * with index tuple header size (see access/itup.h).
66  *
67  * Changing this requires an initdb.
68  */
69 #define INDEX_MAX_KEYS 32
70 
71 /*
72  * Maximum number of columns in a partition key
73  */
74 #define PARTITION_MAX_KEYS 32
75 
76 /*
77  * Decide whether built-in 8-byte types, including float8, int8, and
78  * timestamp, are passed by value. This is on by default if sizeof(Datum) >=
79  * 8 (that is, on 64-bit platforms). If sizeof(Datum) < 8 (32-bit platforms),
80  * this must be off. We keep this here as an option so that it is easy to
81  * test the pass-by-reference code paths on 64-bit platforms.
82  *
83  * Changing this requires an initdb.
84  */
85 #if SIZEOF_VOID_P >= 8
86 #define USE_FLOAT8_BYVAL 1
87 #endif
88 
89 /*
90  * When we don't have native spinlocks, we use semaphores to simulate them.
91  * Decreasing this value reduces consumption of OS resources; increasing it
92  * may improve performance, but supplying a real spinlock implementation is
93  * probably far better.
94  */
95 #define NUM_SPINLOCK_SEMAPHORES 128
96 
97 /*
98  * When we have neither spinlocks nor atomic operations support we're
99  * implementing atomic operations on top of spinlock on top of semaphores. To
100  * be safe against atomic operations while holding a spinlock separate
101  * semaphores have to be used.
102  */
103 #define NUM_ATOMICS_SEMAPHORES 64
104 
105 /*
106  * MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
107  * maximum usable pathname length is one less).
108  *
109  * We'd use a standard system header symbol for this, if there weren't
110  * so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
111  * defined by different "standards", and often have different values
112  * on the same platform! So we just punt and use a reasonably
113  * generous setting here.
114  */
115 #define MAXPGPATH 1024
116 
117 /*
118  * PG_SOMAXCONN: maximum accept-queue length limit passed to
119  * listen(2). You'd think we should use SOMAXCONN from
120  * <sys/socket.h>, but on many systems that symbol is much smaller
121  * than the kernel's actual limit. In any case, this symbol need be
122  * twiddled only if you have a kernel that refuses large limit values,
123  * rather than silently reducing the value to what it can handle
124  * (which is what most if not all Unixen do).
125  */
126 #define PG_SOMAXCONN 10000
127 
128 /*
129  * You can try changing this if you have a machine with bytes of
130  * another size, but no guarantee...
131  */
132 #define BITS_PER_BYTE 8
133 
134 /*
135  * Preferred alignment for disk I/O buffers. On some CPUs, copies between
136  * user space and kernel space are significantly faster if the user buffer
137  * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
138  * a platform-dependent value, but for now we just hard-wire it.
139  */
140 #define ALIGNOF_BUFFER 32
141 
142 /*
143  * If EXEC_BACKEND is defined, the postmaster uses an alternative method for
144  * starting subprocesses: Instead of simply using fork(), as is standard on
145  * Unix platforms, it uses fork()+exec() or something equivalent on Windows,
146  * as well as lots of extra code to bring the required global state to those
147  * new processes. This must be enabled on Windows (because there is no
148  * fork()). On other platforms, it's only useful for verifying those
149  * otherwise Windows-specific code paths.
150  */
151 #if defined(WIN32) && !defined(__CYGWIN__)
152 #define EXEC_BACKEND
153 #endif
154 
155 /*
156  * Define this if your operating system supports link()
157  */
158 #if !defined(WIN32) && !defined(__CYGWIN__)
159 #define HAVE_WORKING_LINK 1
160 #endif
161 
162 /*
163  * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
164  * posix_fadvise() kernel call. Usually the automatic configure tests are
165  * sufficient, but some older Linux distributions had broken versions of
166  * posix_fadvise(). If necessary you can remove the #define here.
167  */
168 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
169 #define USE_POSIX_FADVISE
170 #endif
171 
172 /*
173  * USE_PREFETCH code should be compiled only if we have a way to implement
174  * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
175  * might in future be support for alternative low-level prefetch APIs.
176  * If you change this, you probably need to adjust the error message in
177  * check_effective_io_concurrency.)
178  */
179 #ifdef USE_POSIX_FADVISE
180 #define USE_PREFETCH
181 #endif
182 
183 /*
184  * Default and maximum values for backend_flush_after, bgwriter_flush_after
185  * and checkpoint_flush_after; measured in blocks. Currently, these are
186  * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
187  * we could also enable by default if we have mmap and msync(MS_ASYNC)?
188  */
189 #ifdef HAVE_SYNC_FILE_RANGE
190 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
191 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
192 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
193 #else
194 #define DEFAULT_BACKEND_FLUSH_AFTER 0
195 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
196 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
197 #endif
198 /* upper limit for all three variables */
199 #define WRITEBACK_MAX_PENDING_FLUSHES 256
200 
201 /*
202  * USE_SSL code should be compiled only when compiling with an SSL
203  * implementation.
204  */
205 #ifdef USE_OPENSSL
206 #define USE_SSL
207 #endif
208 
209 /*
210  * This is the default directory in which AF_UNIX socket files are
211  * placed. Caution: changing this risks breaking your existing client
212  * applications, which are likely to continue to look in the old
213  * directory. But if you just hate the idea of sockets in /tmp,
214  * here's where to twiddle it. You can also override this at runtime
215  * with the postmaster's -k switch.
216  *
217  * If set to an empty string, then AF_UNIX sockets are not used by default: A
218  * server will not create an AF_UNIX socket unless the run-time configuration
219  * is changed, a client will connect via TCP/IP by default and will only use
220  * an AF_UNIX socket if one is explicitly specified.
221  *
222  * This is done by default on Windows because there is no good standard
223  * location for AF_UNIX sockets and many installations on Windows don't
224  * support them yet.
225  */
226 #ifndef WIN32
227 #define DEFAULT_PGSOCKET_DIR "/tmp"
228 #else
229 #define DEFAULT_PGSOCKET_DIR ""
230 #endif
231 
232 /*
233  * This is the default event source for Windows event log.
234  */
235 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
236 
237 /*
238  * On PPC machines, decide whether to use the mutex hint bit in LWARX
239  * instructions. Setting the hint bit will slightly improve spinlock
240  * performance on POWER6 and later machines, but does nothing before that,
241  * and will result in illegal-instruction failures on some pre-POWER4
242  * machines. By default we use the hint bit when building for 64-bit PPC,
243  * which should be safe in nearly all cases. You might want to override
244  * this if you are building 32-bit code for a known-recent PPC machine.
245  */
246 #ifdef HAVE_PPC_LWARX_MUTEX_HINT /* must have assembler support in any case */
247 #if defined(__ppc64__) || defined(__powerpc64__)
248 #define USE_PPC_LWARX_MUTEX_HINT
249 #endif
250 #endif
251 
252 /*
253  * On PPC machines, decide whether to use LWSYNC instructions in place of
254  * ISYNC and SYNC. This provides slightly better performance, but will
255  * result in illegal-instruction failures on some pre-POWER4 machines.
256  * By default we use LWSYNC when building for 64-bit PPC, which should be
257  * safe in nearly all cases.
258  */
259 #if defined(__ppc64__) || defined(__powerpc64__)
260 #define USE_PPC_LWSYNC
261 #endif
262 
263 /*
264  * Assumed cache line size. This doesn't affect correctness, but can be used
265  * for low-level optimizations. Currently, this is used to pad some data
266  * structures in xlog.c, to ensure that highly-contended fields are on
267  * different cache lines. Too small a value can hurt performance due to false
268  * sharing, while the only downside of too large a value is a few bytes of
269  * wasted memory. The default is 128, which should be large enough for all
270  * supported platforms.
271  */
272 #define PG_CACHE_LINE_SIZE 128
273 
274 /*
275  *------------------------------------------------------------------------
276  * The following symbols are for enabling debugging code, not for
277  * controlling user-visible features or resource limits.
278  *------------------------------------------------------------------------
279  */
280 
281 /*
282  * Include Valgrind "client requests", mostly in the memory allocator, so
283  * Valgrind understands PostgreSQL memory contexts. This permits detecting
284  * memory errors that Valgrind would not detect on a vanilla build. It also
285  * enables detection of buffer accesses that take place without holding a
286  * buffer pin (or without holding a buffer lock in the case of index access
287  * methods that superimpose their own custom client requests on top of the
288  * generic bufmgr.c requests).
289  *
290  * "make installcheck" is significantly slower under Valgrind. The client
291  * requests fall in hot code paths, so USE_VALGRIND slows execution by a few
292  * percentage points even when not run under Valgrind.
293  *
294  * Do not try to test the server under Valgrind without having built the
295  * server with USE_VALGRIND; else you will get false positives from sinval
296  * messaging (see comments in AddCatcacheInvalidationMessage). It's also
297  * important to use the suppression file src/tools/valgrind.supp to
298  * exclude other known false positives.
299  *
300  * You should normally use MEMORY_CONTEXT_CHECKING with USE_VALGRIND;
301  * instrumentation of repalloc() is inferior without it.
302  */
303 /* #define USE_VALGRIND */
304 
305 /*
306  * Define this to cause pfree()'d memory to be cleared immediately, to
307  * facilitate catching bugs that refer to already-freed values.
308  * Right now, this gets defined automatically if --enable-cassert.
309  */
310 #ifdef USE_ASSERT_CHECKING
311 #define CLOBBER_FREED_MEMORY
312 #endif
313 
314 /*
315  * Define this to check memory allocation errors (scribbling on more
316  * bytes than were allocated). Right now, this gets defined
317  * automatically if --enable-cassert or USE_VALGRIND.
318  */
319 #if defined(USE_ASSERT_CHECKING) || defined(USE_VALGRIND)
320 #define MEMORY_CONTEXT_CHECKING
321 #endif
322 
323 /*
324  * Define this to cause palloc()'d memory to be filled with random data, to
325  * facilitate catching code that depends on the contents of uninitialized
326  * memory. Caution: this is horrendously expensive.
327  */
328 /* #define RANDOMIZE_ALLOCATED_MEMORY */
329 
330 /*
331  * For cache-invalidation debugging, define DISCARD_CACHES_ENABLED to enable
332  * use of the debug_discard_caches GUC to aggressively flush syscache/relcache
333  * entries whenever it's possible to deliver invalidations. See
334  * AcceptInvalidationMessages() in src/backend/utils/cache/inval.c for
335  * details.
336  *
337  * USE_ASSERT_CHECKING builds default to enabling this. It's possible to use
338  * DISCARD_CACHES_ENABLED without a cassert build and the implied
339  * CLOBBER_FREED_MEMORY and MEMORY_CONTEXT_CHECKING options, but it's unlikely
340  * to be as effective at identifying problems.
341  */
342 /* #define DISCARD_CACHES_ENABLED */
343 
344 #if defined(USE_ASSERT_CHECKING) && !defined(DISCARD_CACHES_ENABLED)
345 #define DISCARD_CACHES_ENABLED
346 #endif
347 
348 /*
349  * Backwards compatibility for the older compile-time-only clobber-cache
350  * macros.
351  */
352 #if !defined(DISCARD_CACHES_ENABLED) && (defined(CLOBBER_CACHE_ALWAYS) || defined(CLOBBER_CACHE_RECURSIVELY))
353 #define DISCARD_CACHES_ENABLED
354 #endif
355 
356 /*
357  * Recover memory used for relcache entries when invalidated. See
358  * RelationBuildDescr() in src/backend/utils/cache/relcache.c.
359  *
360  * This is active automatically for clobber-cache builds when clobbering is
361  * active, but can be overridden here by explicitly defining
362  * RECOVER_RELATION_BUILD_MEMORY. Define to 1 to always free relation cache
363  * memory even when clobber is off, or to 0 to never free relation cache
364  * memory even when clobbering is on.
365  */
366  /* #define RECOVER_RELATION_BUILD_MEMORY 0 */ /* Force disable */
367  /* #define RECOVER_RELATION_BUILD_MEMORY 1 */ /* Force enable */
368 
369 /*
370  * Define this to force all parse and plan trees to be passed through
371  * copyObject(), to facilitate catching errors and omissions in
372  * copyObject().
373  */
374 /* #define COPY_PARSE_PLAN_TREES */
375 
376 /*
377  * Define this to force all parse and plan trees to be passed through
378  * outfuncs.c/readfuncs.c, to facilitate catching errors and omissions in
379  * those modules.
380  */
381 /* #define WRITE_READ_PARSE_PLAN_TREES */
382 
383 /*
384  * Define this to force all raw parse trees for DML statements to be scanned
385  * by raw_expression_tree_walker(), to facilitate catching errors and
386  * omissions in that function.
387  */
388 /* #define RAW_EXPRESSION_COVERAGE_TEST */
389 
390 /*
391  * Enable debugging print statements for lock-related operations.
392  */
393 /* #define LOCK_DEBUG */
394 
395 /*
396  * Enable debugging print statements for WAL-related operations; see
397  * also the wal_debug GUC var.
398  */
399 /* #define WAL_DEBUG */
400 
401 /*
402  * Enable tracing of resource consumption during sort operations;
403  * see also the trace_sort GUC var. For 8.1 this is enabled by default.
404  */
405 #define TRACE_SORT 1
406 
407 /*
408  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
409  */
410 /* #define TRACE_SYNCSCAN */