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Commitf9e497d

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Doco updates for change to handling of INTERNAL function
entries (prosrc is now name of C-level function).
1 parent77d3355 commitf9e497d

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2 files changed

+51
-27
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2 files changed

+51
-27
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‎src/man/catalogs.3‎

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
.\" This is -*-nroff-*-
22
.\" XXX standard disclaimer belongs here....
3-
.\" $Header: /cvsroot/pgsql/src/man/Attic/catalogs.3,v 1.5 1998/03/25 01:54:49 momjian Exp $
3+
.\" $Header: /cvsroot/pgsql/src/man/Attic/catalogs.3,v 1.6 1999/05/20 02:44:53 tgl Exp $
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.TH "SYSTEM CATALOGS" INTRO 03/13/94 PostgreSQL PostgreSQL
55
.SH "Section 7 - System Catalogs"
66
.deLS
@@ -316,8 +316,12 @@ pg_proc
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size) */
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int4 prooutin_ratio/* size of the function's output as a
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percentage of the size of the input */
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text prosrc/* function definition (postquel only) */
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bytea probin/* path to object file (C only) */
319+
text prosrc/* function definition:
320+
INTERNAL function: actual C name of function
321+
C function: currently, this field is unused
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SQL function: text of query(s)
323+
PL function: text in procedural language */
324+
bytea probin/* path to object file (C functions only) */
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.fi
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.nfM
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pg_language

‎src/man/create_function.l‎

Lines changed: 44 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
.\" This is -*-nroff-*-
22
.\" XXX standard disclaimer belongs here....
3-
.\" $Header: /cvsroot/pgsql/src/man/Attic/create_function.l,v 1.10 1998/06/24 13:21:24 momjian Exp $
3+
.\" $Header: /cvsroot/pgsql/src/man/Attic/create_function.l,v 1.11 1999/05/20 02:44:53 tgl Exp $
44
.TH "CREATE FUNCTION" SQL 11/05/95 PostgreSQL PostgreSQL
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.SH "NAME"
66
create function - define a new function
@@ -9,8 +9,9 @@ create function - define a new function
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\fBcreatefunction\fP function_name
1010
\fB(\fP[type1 {, type-n}]\fB)\fP
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\fBreturns\fP type-r
12-
\fBas\fP {'/full/path/to/objectfile' | 'sql-queries'}
13-
\fBlanguage\fP {'c'\'sql'\'internal'\'plname'}
12+
\fBas\fP { '/full/path/to/objectfile' | 'sql-queries' |
13+
'builtin-function-name' | 'pl-program-text' }
14+
\fBlanguage\fP { 'c' | 'sql' | 'internal' | 'plname' }
1415
.fi
1516
.SH "DESCRIPTION"
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With this command, a Postgres user can register a function with Postgres.
@@ -35,9 +36,8 @@ or
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.IR"plname"
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is the language name of a created procedural language. See
3738
create_language(l) for details.)
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(The
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.IR"arg is"
40-
clause may be left out if the function has no arguments, or
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(The argument list
40+
may be left out if the function has no arguments, or
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alternatively the argument list may be left empty.)
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The input types may be base or complex types, or
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.IR opaque.
@@ -54,32 +54,43 @@ modifier indicates that the function will return a set of items,
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rather than a single item.
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The
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.IR as
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clause of the command is treated differently for C and SQL
58-
functions, as explained below.
57+
clause of the command is treated differently depending on the language,
58+
as explained below.
59+
.SH "INTERNAL FUNCTIONS"
60+
Internal functions are functions written in C which have been statically
61+
linked into the postgres backend process. The
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.BR as
63+
clause gives the C-language name of the function, which need not be the
64+
same as the name being declared for SQL use. (For reasons of backwards
65+
compatibility, an empty
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.BR as
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string is accepted as meaning that the C-language function name is the
68+
same as the SQL name.) Normally, all internal functions present in the
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backend are declared as SQL functions during database initialization,
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but a user could use
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.BR"create function"
72+
to create additional alias names for an internal function.
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.SH "C FUNCTIONS"
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Functions written in C can be defined to Postgres, which will dynamically
61-
load them into its address space. The loading happens either using
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load them into its address space. The
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.IR as
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clause gives the full path name of the object file that contains the
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function. This file is loaded either using
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.IR load(l)
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or automatically the first time the function is necessary for
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execution. Repeated execution of a function will cause negligible
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additional overhead, as the function will remain in a main memory
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cache.
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.PP
68-
Internal functions are functions written in C which have been statically
69-
linked into the postgres backend process. The
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.BR as
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clause must still be specified when defining an internal function but
72-
the contents are ignored.
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.SH "Writing C Functions"
74-
The body ofa C function following
85+
Fora C function, the string following
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.BR as
7687
should be the
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.BR"FULL PATH"
78-
of the object code(.ofile) for the function, bracketed by quotation
89+
of the object code file for the function, bracketed by quotation
7990
marks. (Postgres will not compile a function automatically - it must
8091
be compiled before it is used in a
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.BR"define function"
82-
command.)
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.BR"create function"
93+
command. See below for additional information.)
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.PP
8495
C functions with base type arguments can be written in a
8596
straightforward fashion. The C equivalents of built-in Postgres types
@@ -297,7 +308,7 @@ on. If an argument is complex, then a \*(lqdot\*(rq notation may be
297308
used to access attributes of the argument (e.g.\*(lq$1.emp\*(rq), or
298309
to invoke functions via a nested-dot syntax.
299310
.SH "PL FUNCTIONS"
300-
Procedural languages aren'tbuiltin to Postgres. They are offered
311+
Procedural languages aren'tbuilt into Postgres. They are offered
301312
by loadable modules. Please refer to the documentation for the
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PL in question for details about the syntax and how the
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.IR"as"
@@ -400,10 +411,11 @@ A function may also have the same name as an attribute. In the case
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that there is an ambiguity between a function on a complex type and
401412
an attribute of the complex type, the attribute will always be used.
402413
.SH "RESTRICTIONS"
403-
The name of the C function must be a legal C function name, and the
404-
name of the function in C code must be exactly the same as the name
405-
used in
406-
.BR"create function".
414+
For functions written in C, the SQL name declared in
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.BR"create function"
416+
must be exactly the same as the actual name of the function in the
417+
C code (hence it must be a legal C function name).
418+
.PP
407419
There is a subtle implication of this restriction: while the
408420
dynamic loading routines in most operating systems are more than
409421
happy to allow you to load any number of shared libraries that
@@ -422,6 +434,14 @@ define a set of C functions with different names and then define
422434
a set of identically-named SQL function wrappers that take the
423435
appropriate argument types and call the matching C function.
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.PP
437+
Another solution is not to use dynamic loading, but to link your
438+
functions into the backend statically and declare them as INTERNAL
439+
functions. Then, the functions must all have distinct C names but
440+
they can be declared with the same SQL names (as long as their
441+
argument types differ, of course). This way avoids the overhead of
442+
an SQL wrapper function, at the cost of more effort to prepare a
443+
custom backend executable.
444+
.PP
425445
.IR opaque
426446
cannot be given as an argument to a SQL function.
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.SH "BUGS"

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