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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) 1996-2023, 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  * You can try changing this if you have a machine with bytes of
119  * another size, but no guarantee...
120  */
121 #define BITS_PER_BYTE 8
122 
123 /*
124  * Preferred alignment for disk I/O buffers. On some CPUs, copies between
125  * user space and kernel space are significantly faster if the user buffer
126  * is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
127  * a platform-dependent value, but for now we just hard-wire it.
128  */
129 #define ALIGNOF_BUFFER 32
130 
131 /*
132  * If EXEC_BACKEND is defined, the postmaster uses an alternative method for
133  * starting subprocesses: Instead of simply using fork(), as is standard on
134  * Unix platforms, it uses fork()+exec() or something equivalent on Windows,
135  * as well as lots of extra code to bring the required global state to those
136  * new processes. This must be enabled on Windows (because there is no
137  * fork()). On other platforms, it's only useful for verifying those
138  * otherwise Windows-specific code paths.
139  */
140 #if defined(WIN32) && !defined(__CYGWIN__)
141 #define EXEC_BACKEND
142 #endif
143 
144 /*
145  * USE_POSIX_FADVISE controls whether Postgres will attempt to use the
146  * posix_fadvise() kernel call. Usually the automatic configure tests are
147  * sufficient, but some older Linux distributions had broken versions of
148  * posix_fadvise(). If necessary you can remove the #define here.
149  */
150 #if HAVE_DECL_POSIX_FADVISE && defined(HAVE_POSIX_FADVISE)
151 #define USE_POSIX_FADVISE
152 #endif
153 
154 /*
155  * USE_PREFETCH code should be compiled only if we have a way to implement
156  * prefetching. (This is decoupled from USE_POSIX_FADVISE because there
157  * might in future be support for alternative low-level prefetch APIs.
158  * If you change this, you probably need to adjust the error message in
159  * check_effective_io_concurrency.)
160  */
161 #ifdef USE_POSIX_FADVISE
162 #define USE_PREFETCH
163 #endif
164 
165 /*
166  * Default and maximum values for backend_flush_after, bgwriter_flush_after
167  * and checkpoint_flush_after; measured in blocks. Currently, these are
168  * enabled by default if sync_file_range() exists, ie, only on Linux. Perhaps
169  * we could also enable by default if we have mmap and msync(MS_ASYNC)?
170  */
171 #ifdef HAVE_SYNC_FILE_RANGE
172 #define DEFAULT_BACKEND_FLUSH_AFTER 0 /* never enabled by default */
173 #define DEFAULT_BGWRITER_FLUSH_AFTER 64
174 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32
175 #else
176 #define DEFAULT_BACKEND_FLUSH_AFTER 0
177 #define DEFAULT_BGWRITER_FLUSH_AFTER 0
178 #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
179 #endif
180 /* upper limit for all three variables */
181 #define WRITEBACK_MAX_PENDING_FLUSHES 256
182 
183 /*
184  * USE_SSL code should be compiled only when compiling with an SSL
185  * implementation.
186  */
187 #ifdef USE_OPENSSL
188 #define USE_SSL
189 #endif
190 
191 /*
192  * This is the default directory in which AF_UNIX socket files are
193  * placed. Caution: changing this risks breaking your existing client
194  * applications, which are likely to continue to look in the old
195  * directory. But if you just hate the idea of sockets in /tmp,
196  * here's where to twiddle it. You can also override this at runtime
197  * with the postmaster's -k switch.
198  *
199  * If set to an empty string, then AF_UNIX sockets are not used by default: A
200  * server will not create an AF_UNIX socket unless the run-time configuration
201  * is changed, a client will connect via TCP/IP by default and will only use
202  * an AF_UNIX socket if one is explicitly specified.
203  *
204  * This is done by default on Windows because there is no good standard
205  * location for AF_UNIX sockets and many installations on Windows don't
206  * support them yet.
207  */
208 #ifndef WIN32
209 #define DEFAULT_PGSOCKET_DIR "/tmp"
210 #else
211 #define DEFAULT_PGSOCKET_DIR ""
212 #endif
213 
214 /*
215  * This is the default event source for Windows event log.
216  */
217 #define DEFAULT_EVENT_SOURCE "PostgreSQL"
218 
219 /*
220  * Assumed cache line size. This doesn't affect correctness, but can be used
221  * for low-level optimizations. Currently, this is used to pad some data
222  * structures in xlog.c, to ensure that highly-contended fields are on
223  * different cache lines. Too small a value can hurt performance due to false
224  * sharing, while the only downside of too large a value is a few bytes of
225  * wasted memory. The default is 128, which should be large enough for all
226  * supported platforms.
227  */
228 #define PG_CACHE_LINE_SIZE 128
229 
230 /*
231  *------------------------------------------------------------------------
232  * The following symbols are for enabling debugging code, not for
233  * controlling user-visible features or resource limits.
234  *------------------------------------------------------------------------
235  */
236 
237 /*
238  * Include Valgrind "client requests", mostly in the memory allocator, so
239  * Valgrind understands PostgreSQL memory contexts. This permits detecting
240  * memory errors that Valgrind would not detect on a vanilla build. It also
241  * enables detection of buffer accesses that take place without holding a
242  * buffer pin (or without holding a buffer lock in the case of index access
243  * methods that superimpose their own custom client requests on top of the
244  * generic bufmgr.c requests).
245  *
246  * "make installcheck" is significantly slower under Valgrind. The client
247  * requests fall in hot code paths, so USE_VALGRIND slows execution by a few
248  * percentage points even when not run under Valgrind.
249  *
250  * Do not try to test the server under Valgrind without having built the
251  * server with USE_VALGRIND; else you will get false positives from sinval
252  * messaging (see comments in AddCatcacheInvalidationMessage). It's also
253  * important to use the suppression file src/tools/valgrind.supp to
254  * exclude other known false positives.
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  * For cache-invalidation debugging, define DISCARD_CACHES_ENABLED to enable
288  * use of the debug_discard_caches GUC to aggressively flush syscache/relcache
289  * entries whenever it's possible to deliver invalidations. See
290  * AcceptInvalidationMessages() in src/backend/utils/cache/inval.c for
291  * details.
292  *
293  * USE_ASSERT_CHECKING builds default to enabling this. It's possible to use
294  * DISCARD_CACHES_ENABLED without a cassert build and the implied
295  * CLOBBER_FREED_MEMORY and MEMORY_CONTEXT_CHECKING options, but it's unlikely
296  * to be as effective at identifying problems.
297  */
298 /* #define DISCARD_CACHES_ENABLED */
299 
300 #if defined(USE_ASSERT_CHECKING) && !defined(DISCARD_CACHES_ENABLED)
301 #define DISCARD_CACHES_ENABLED
302 #endif
303 
304 /*
305  * Backwards compatibility for the older compile-time-only clobber-cache
306  * macros.
307  */
308 #if !defined(DISCARD_CACHES_ENABLED) && (defined(CLOBBER_CACHE_ALWAYS) || defined(CLOBBER_CACHE_RECURSIVELY))
309 #define DISCARD_CACHES_ENABLED
310 #endif
311 
312 /*
313  * Recover memory used for relcache entries when invalidated. See
314  * RelationBuildDescr() in src/backend/utils/cache/relcache.c.
315  *
316  * This is active automatically for clobber-cache builds when clobbering is
317  * active, but can be overridden here by explicitly defining
318  * RECOVER_RELATION_BUILD_MEMORY. Define to 1 to always free relation cache
319  * memory even when clobber is off, or to 0 to never free relation cache
320  * memory even when clobbering is on.
321  */
322  /* #define RECOVER_RELATION_BUILD_MEMORY 0 */ /* Force disable */
323  /* #define RECOVER_RELATION_BUILD_MEMORY 1 */ /* Force enable */
324 
325 /*
326  * Define this to force all parse and plan trees to be passed through
327  * copyObject(), to facilitate catching errors and omissions in
328  * copyObject().
329  */
330 /* #define COPY_PARSE_PLAN_TREES */
331 
332 /*
333  * Define this to force all parse and plan trees to be passed through
334  * outfuncs.c/readfuncs.c, to facilitate catching errors and omissions in
335  * those modules.
336  */
337 /* #define WRITE_READ_PARSE_PLAN_TREES */
338 
339 /*
340  * Define this to force all raw parse trees for DML statements to be scanned
341  * by raw_expression_tree_walker(), to facilitate catching errors and
342  * omissions in that function.
343  */
344 /* #define RAW_EXPRESSION_COVERAGE_TEST */
345 
346 /*
347  * Enable debugging print statements for lock-related operations.
348  */
349 /* #define LOCK_DEBUG */
350 
351 /*
352  * Enable debugging print statements for WAL-related operations; see
353  * also the wal_debug GUC var.
354  */
355 /* #define WAL_DEBUG */
356 
357 /*
358  * Enable tracing of resource consumption during sort operations;
359  * see also the trace_sort GUC var. For 8.1 this is enabled by default.
360  */
361 #define TRACE_SORT 1
362 
363 /*
364  * Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
365  */
366 /* #define TRACE_SYNCSCAN */