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a04a423599
when multiple backends are scanning the same relation concurrently, each page is (ideally) read only once. Jeff Davis, with review by Heikki and Tom.
263 lines
8.7 KiB
C
263 lines
8.7 KiB
C
/*------------------------------------------------------------------------
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* PostgreSQL manual configuration settings
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*
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* This file contains various configuration symbols and limits. In
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* all cases, changing them is only useful in very rare situations or
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* for developers. If you edit any of these, be sure to do a *full*
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* rebuild (and an initdb if noted).
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*
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* $PostgreSQL: pgsql/src/include/pg_config_manual.h,v 1.27 2007/06/08 18:23:53 tgl Exp $
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*------------------------------------------------------------------------
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*/
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/*
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* Size of a disk block --- this also limits the size of a tuple. You
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* can set it bigger if you need bigger tuples (although TOAST should
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* reduce the need to have large tuples, since fields can be spread
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* across multiple tuples).
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*
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* BLCKSZ must be a power of 2. The maximum possible value of BLCKSZ
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* is currently 2^15 (32768). This is determined by the 15-bit widths
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* of the lp_off and lp_len fields in ItemIdData (see
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* include/storage/itemid.h).
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*
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* Changing BLCKSZ requires an initdb.
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*/
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#define BLCKSZ 8192
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/*
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* RELSEG_SIZE is the maximum number of blocks allowed in one disk
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* file. Thus, the maximum size of a single file is RELSEG_SIZE *
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* BLCKSZ; relations bigger than that are divided into multiple files.
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*
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* RELSEG_SIZE * BLCKSZ must be less than your OS' limit on file size.
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* This is often 2 GB or 4GB in a 32-bit operating system, unless you
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* have large file support enabled. By default, we make the limit 1
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* GB to avoid any possible integer-overflow problems within the OS.
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* A limit smaller than necessary only means we divide a large
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* relation into more chunks than necessary, so it seems best to err
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* in the direction of a small limit. (Besides, a power-of-2 value
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* saves a few cycles in md.c.)
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*
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* Changing RELSEG_SIZE requires an initdb.
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*/
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#define RELSEG_SIZE (0x40000000 / BLCKSZ)
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/*
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* Size of a WAL file block. This need have no particular relation to BLCKSZ.
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* XLOG_BLCKSZ must be a power of 2, and if your system supports O_DIRECT I/O,
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* XLOG_BLCKSZ must be a multiple of the alignment requirement for direct-I/O
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* buffers, else direct I/O may fail.
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*
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* Changing XLOG_BLCKSZ requires an initdb.
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*/
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#define XLOG_BLCKSZ 8192
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/*
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* XLOG_SEG_SIZE is the size of a single WAL file. This must be a power of 2
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* and larger than XLOG_BLCKSZ (preferably, a great deal larger than
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* XLOG_BLCKSZ).
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*
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* Changing XLOG_SEG_SIZE requires an initdb.
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*/
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#define XLOG_SEG_SIZE (16*1024*1024)
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/*
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* Maximum length for identifiers (e.g. table names, column names,
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* function names). It must be a multiple of sizeof(int) (typically
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* 4).
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*
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* Changing this requires an initdb.
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*/
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#define NAMEDATALEN 64
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/*
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* Maximum number of arguments to a function.
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*
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* The minimum value is 8 (index cost estimation uses 8-argument functions).
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* The maximum possible value is around 600 (limited by index tuple size in
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* pg_proc's index; BLCKSZ larger than 8K would allow more). Values larger
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* than needed will waste memory and processing time, but do not directly
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* cost disk space.
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*
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* Changing this does not require an initdb, but it does require a full
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* backend recompile (including any user-defined C functions).
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*/
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#define FUNC_MAX_ARGS 100
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/*
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* Maximum number of columns in an index. There is little point in making
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* this anything but a multiple of 32, because the main cost is associated
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* with index tuple header size (see access/itup.h).
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*
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* Changing this requires an initdb.
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*/
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#define INDEX_MAX_KEYS 32
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/*
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* Number of spare LWLocks to allocate for user-defined add-on code.
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*/
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#define NUM_USER_DEFINED_LWLOCKS 4
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/*
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* Define this to make libpgtcl's "pg_result -assign" command process
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* C-style backslash sequences in returned tuple data and convert
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* PostgreSQL array values into Tcl lists. CAUTION: This conversion
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* is *wrong* unless you install the routines in
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* contrib/string/string_io to make the server produce C-style
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* backslash sequences in the first place.
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*/
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/* #define TCL_ARRAYS */
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/*
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* Define this if you want psql to _always_ ask for a username and a
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* password for password authentication.
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*/
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/* #define PSQL_ALWAYS_GET_PASSWORDS */
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/*
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* Define this if you want to allow the lo_import and lo_export SQL
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* functions to be executed by ordinary users. By default these
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* functions are only available to the Postgres superuser. CAUTION:
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* These functions are SECURITY HOLES since they can read and write
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* any file that the PostgreSQL server has permission to access. If
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* you turn this on, don't say we didn't warn you.
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*/
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/* #define ALLOW_DANGEROUS_LO_FUNCTIONS */
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/*
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* MAXPGPATH: standard size of a pathname buffer in PostgreSQL (hence,
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* maximum usable pathname length is one less).
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*
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* We'd use a standard system header symbol for this, if there weren't
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* so many to choose from: MAXPATHLEN, MAX_PATH, PATH_MAX are all
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* defined by different "standards", and often have different values
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* on the same platform! So we just punt and use a reasonably
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* generous setting here.
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*/
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#define MAXPGPATH 1024
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/*
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* PG_SOMAXCONN: maximum accept-queue length limit passed to
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* listen(2). You'd think we should use SOMAXCONN from
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* <sys/socket.h>, but on many systems that symbol is much smaller
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* than the kernel's actual limit. In any case, this symbol need be
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* twiddled only if you have a kernel that refuses large limit values,
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* rather than silently reducing the value to what it can handle
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* (which is what most if not all Unixen do).
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*/
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#define PG_SOMAXCONN 10000
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/*
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* You can try changing this if you have a machine with bytes of
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* another size, but no guarantee...
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*/
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#define BITS_PER_BYTE 8
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/*
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* Preferred alignment for disk I/O buffers. On some CPUs, copies between
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* user space and kernel space are significantly faster if the user buffer
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* is aligned on a larger-than-MAXALIGN boundary. Ideally this should be
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* a platform-dependent value, but for now we just hard-wire it.
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*/
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#define ALIGNOF_BUFFER 32
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/*
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* Disable UNIX sockets for those operating system.
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*/
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#if defined(WIN32)
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#undef HAVE_UNIX_SOCKETS
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#endif
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/*
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* Define this if your operating system supports link()
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*/
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#if !defined(WIN32) && !defined(__CYGWIN__)
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#define HAVE_WORKING_LINK 1
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#endif
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/*
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* This is the default directory in which AF_UNIX socket files are
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* placed. Caution: changing this risks breaking your existing client
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* applications, which are likely to continue to look in the old
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* directory. But if you just hate the idea of sockets in /tmp,
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* here's where to twiddle it. You can also override this at runtime
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* with the postmaster's -k switch.
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*/
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#define DEFAULT_PGSOCKET_DIR "/tmp"
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/*
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* The random() function is expected to yield values between 0 and
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* MAX_RANDOM_VALUE. Currently, all known implementations yield
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* 0..2^31-1, so we just hardwire this constant. We could do a
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* configure test if it proves to be necessary. CAUTION: Think not to
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* replace this with RAND_MAX. RAND_MAX defines the maximum value of
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* the older rand() function, which is often different from --- and
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* considerably inferior to --- random().
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*/
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#define MAX_RANDOM_VALUE (0x7FFFFFFF)
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/*
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*------------------------------------------------------------------------
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* The following symbols are for enabling debugging code, not for
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* controlling user-visible features or resource limits.
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*------------------------------------------------------------------------
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*/
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/*
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* Define this to cause pfree()'d memory to be cleared immediately, to
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* facilitate catching bugs that refer to already-freed values. XXX
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* Right now, this gets defined automatically if --enable-cassert. In
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* the long term it probably doesn't need to be on by default.
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*/
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#ifdef USE_ASSERT_CHECKING
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#define CLOBBER_FREED_MEMORY
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#endif
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/*
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* Define this to check memory allocation errors (scribbling on more
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* bytes than were allocated). Right now, this gets defined
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* automatically if --enable-cassert. In the long term it probably
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* doesn't need to be on by default.
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*/
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#ifdef USE_ASSERT_CHECKING
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#define MEMORY_CONTEXT_CHECKING
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#endif
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/*
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* Define this to force all parse and plan trees to be passed through
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* copyObject(), to facilitate catching errors and omissions in
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* copyObject().
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*/
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/* #define COPY_PARSE_PLAN_TREES */
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/*
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* Enable debugging print statements for lock-related operations.
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*/
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/* #define LOCK_DEBUG */
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/*
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* Enable debugging print statements for WAL-related operations; see
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* also the wal_debug GUC var.
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*/
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/* #define WAL_DEBUG */
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/*
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* Enable tracing of resource consumption during sort operations;
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* see also the trace_sort GUC var. For 8.1 this is enabled by default.
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*/
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#define TRACE_SORT 1
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/*
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* Enable tracing of syncscan operations (see also the trace_syncscan GUC var).
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*/
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/* #define TRACE_SYNCSCAN */
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/*
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* Other debug #defines (documentation, anyone?)
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*/
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/* #define HEAPDEBUGALL */
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/* #define ACLDEBUG */
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/* #define RTDEBUG */
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