mirror of https://github.com/postgres/postgres
Bruce Momjian
25 years ago
parent
b33c66234e
commit
5af4855383
@ -0,0 +1,48 @@ |
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subdir = contrib/dblink
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top_builddir = ../..
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include $(top_builddir)/src/Makefile.global |
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include $(top_builddir)/src/Makefile.shlib |
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include_srcdir = $(top_builddir)/src/include
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NAME := dblink
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SONAME := $(NAME)$(DLSUFFIX)
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override CFLAGS += -I$(srcdir)
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override CFLAGS += -I$(include_srcdir)
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override CFLAGS += -I$(libpq_srcdir)
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override CFLAGS += $(CFLAGS_SL)
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OBJS = $(NAME).o
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all: $(OBJS) $(SONAME) $(NAME).sql |
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$(OBJS): $(NAME).c |
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$(CC) -o $@ -c $(CFLAGS) $<
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$(SONAME): $(OBJS) |
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$(LD) -o $@ -Bshareable $(libpq) $<
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$(NAME).sql: $(NAME).sql.in |
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sed -e 's:MODULE_PATHNAME:$(libdir)/contrib/$(SONAME):g' < $< > $@
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install: all installdirs |
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$(INSTALL_DATA) README.$(NAME) $(docdir)/contrib
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$(INSTALL_DATA) $(NAME).sql $(datadir)/contrib
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$(INSTALL_SHLIB) $(SONAME) $(libdir)/contrib
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installdirs: |
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$(mkinstalldirs) $(docdir)/contrib $(datadir)/contrib $(libdir)/contrib
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uninstall: |
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rm -rf $(docdir)/contrib/README.$(NAME) $(datadir)/contrib/$(NAME).sql $(libdir)/contrib/$(SONAME)
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clean distclean maintainer-clean: |
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rm -f $(SONAME) *.o *.sql
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depend dep: |
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$(CC) -MM -MG $(CFLAGS) *.c > depend
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ifeq (depend,$(wildcard depend)) |
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include depend |
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endif |
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@ -0,0 +1,157 @@ |
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/* |
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* dblink |
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* |
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* Functions returning results from a remote database |
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* |
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* Copyright (c) Joseph Conway <joe.conway@mail.com>, 2001; |
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* |
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* Permission to use, copy, modify, and distribute this software and its |
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* documentation for any purpose, without fee, and without a written agreement |
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* is hereby granted, provided that the above copyright notice and this |
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* paragraph and the following two paragraphs appear in all copies. |
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* |
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* IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR |
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING |
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS |
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* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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* |
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* THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIMS ANY WARRANTIES, |
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY |
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS |
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* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO |
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. |
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* |
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*/ |
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|
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Version 0.2 (29 May, 2001): |
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Function to test returning data set from remote database |
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Tested under Linux (Red Hat 6.2 and 7.0) and PostgreSQL 7.1 and 7.2devel |
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Release Notes: |
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Version 0.2 |
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- initial release |
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Installation: |
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Place these files in a directory called 'dblink' under 'contrib' in the PostgreSQL source tree. Then run: |
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make |
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make install |
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You can use dblink.sql to create the functions in your database of choice, e.g. |
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psql -U postgres template1 < dblink.sql |
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installs following functions into database template1: |
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dblink() - returns a pointer to results from remote query |
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dblink_tok() - extracts and returns individual field results |
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Documentation |
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================================================================== |
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Name |
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dblink -- Returns a pointer to a data set from a remote database |
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Synopsis |
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dblink(text connstr, text sql) |
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Inputs |
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connstr |
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standard libpq format connection srting, |
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e.g. "hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd" |
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sql |
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sql statement that you wish to execute on the remote host |
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e.g. "select * from pg_class" |
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Outputs |
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Returns setof int (pointer) |
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Example usage |
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select dblink('hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd','select f1, f2 from mytable'); |
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================================================================== |
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Name |
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dblink_tok -- Returns individual select field results from a dblink remote query |
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Synopsis |
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dblink_tok(int pointer, int fnumber) |
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Inputs |
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pointer |
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a pointer returned by a call to dblink() |
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fnumber |
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the ordinal position (zero based) of the field to be returned from the dblink result set |
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Outputs |
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Returns text |
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Example usage |
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select dblink_tok(t1.dblink_p,0) as f1, dblink_tok(t1.dblink_p,1) as f2 |
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from (select dblink('hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd' |
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,'select f1, f2 from mytable') as dblink_p) as t1; |
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================================================================== |
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NOTE: If you need to provide selection criteria in a WHERE clause, it is necessary |
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to 'fake' a UNION, e.g. |
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select |
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dblink_tok(t1.dblink_p,0) as f1 |
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,dblink_tok(t1.dblink_p,1) as f2 |
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from |
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( |
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select dblink( |
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'hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd' |
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,'select f1, f2 from mytable' |
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) as dblink_p |
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union |
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select null,null where false |
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) as t1 |
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where |
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f1 = 'mycriteria'; |
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in order to work around an issue with the query optimizer. A more convenient way to approach |
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this problem is to create a view: |
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create view myremotetable as |
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select |
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dblink_tok(t1.dblink_p,0) as f1 |
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,dblink_tok(t1.dblink_p,1) as f2 |
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from |
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( |
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select dblink( |
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'hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd' |
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,'select f1, f2 from mytable' |
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) as dblink_p |
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union |
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select null,null where false |
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) as t1; |
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Then you can simply write: |
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select f1,f2 from myremotetable where f1 = 'mycriteria'; |
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================================================================== |
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-- Joe Conway |
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@ -0,0 +1,276 @@ |
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/*
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* dblink.c |
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* |
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* Functions returning results from a remote database |
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* |
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* Copyright (c) Joseph Conway <joe.conway@mail.com>, 2001; |
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*
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* Permission to use, copy, modify, and distribute this software and its |
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* documentation for any purpose, without fee, and without a written agreement |
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* is hereby granted, provided that the above copyright notice and this |
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* paragraph and the following two paragraphs appear in all copies. |
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*
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* IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR |
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* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING |
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* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS |
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* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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*
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* THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIMS ANY WARRANTIES, |
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY |
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* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS |
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* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO |
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* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. |
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* |
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*/ |
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#include "dblink.h" |
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PG_FUNCTION_INFO_V1(dblink); |
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Datum |
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dblink(PG_FUNCTION_ARGS) |
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{ |
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PGconn *conn = NULL; |
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PGresult *res = NULL; |
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dblink_results *results; |
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char *optstr; |
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char *sqlstatement; |
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char *curstr = "DECLARE mycursor CURSOR FOR "; |
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char *execstatement; |
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char *msg; |
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int ntuples = 0; |
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ReturnSetInfo *rsi; |
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if (PG_ARGISNULL(0) || PG_ARGISNULL(1)) { |
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elog(ERROR, "dblink: NULL arguments are not permitted"); |
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} |
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if (fcinfo->resultinfo == NULL || ! IsA(fcinfo->resultinfo, ReturnSetInfo)) { |
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elog(ERROR, "dblink: function called in context that does not accept a set result"); |
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} |
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optstr = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(0)))); |
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sqlstatement = DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(PG_GETARG_TEXT_P(1)))); |
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if (fcinfo->flinfo->fn_extra == NULL) { |
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conn = PQconnectdb(optstr); |
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if (PQstatus(conn) == CONNECTION_BAD) |
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{ |
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msg = PQerrorMessage(conn); |
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PQfinish(conn); |
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elog(ERROR, "dblink: connection error: %s", msg); |
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} |
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res = PQexec(conn, "BEGIN"); |
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if (PQresultStatus(res) != PGRES_COMMAND_OK) |
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{ |
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msg = PQerrorMessage(conn); |
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PQclear(res); |
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PQfinish(conn); |
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elog(ERROR, "dblink: begin error: %s", msg); |
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} |
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PQclear(res); |
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execstatement = (char *) palloc(strlen(curstr) + strlen(sqlstatement) + 1); |
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if (execstatement != NULL) { |
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strcpy(execstatement, curstr); |
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strcat(execstatement, sqlstatement); |
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strcat(execstatement, "\0"); |
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} else { |
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elog(ERROR, "dblink: insufficient memory" ); |
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} |
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res = PQexec(conn, execstatement); |
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if (!res || (PQresultStatus(res) != PGRES_COMMAND_OK && PQresultStatus(res) != PGRES_TUPLES_OK)) |
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{ |
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msg = PQerrorMessage(conn); |
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PQclear(res); |
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PQfinish(conn); |
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elog(ERROR, "dblink: sql error: %s", msg); |
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} else { |
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/*
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* got results, start fetching them |
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*/ |
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PQclear(res); |
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res = PQexec(conn, "FETCH ALL in mycursor"); |
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if (!res || PQresultStatus(res) != PGRES_TUPLES_OK) { |
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msg = PQerrorMessage(conn); |
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PQclear(res); |
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PQfinish(conn); |
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elog(ERROR, "dblink: sql error: %s", msg); |
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} |
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ntuples = PQntuples(res); |
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if (ntuples > 0) { |
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results = init_dblink_results(fcinfo->flinfo->fn_mcxt); |
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results->tup_num = 0; |
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results->res = res; |
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res = NULL; |
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(dblink_results *) fcinfo->flinfo->fn_extra = results; |
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results = NULL; |
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results = fcinfo->flinfo->fn_extra; |
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/* close the cursor */ |
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res = PQexec(conn, "CLOSE mycursor"); |
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PQclear(res); |
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/* commit the transaction */ |
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res = PQexec(conn, "COMMIT"); |
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PQclear(res); |
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/* close the connection to the database and cleanup */ |
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PQfinish(conn); |
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rsi = (ReturnSetInfo *)fcinfo->resultinfo; |
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rsi->isDone = ExprMultipleResult; |
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PG_RETURN_POINTER(results); |
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} else { |
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PQclear(res); |
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/* close the cursor */ |
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res = PQexec(conn, "CLOSE mycursor"); |
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PQclear(res); |
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/* commit the transaction */ |
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res = PQexec(conn, "COMMIT"); |
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PQclear(res); |
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/* close the connection to the database and cleanup */ |
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PQfinish(conn); |
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rsi = (ReturnSetInfo *)fcinfo->resultinfo; |
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rsi->isDone = ExprEndResult ; |
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PG_RETURN_NULL(); |
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} |
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} |
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} else { |
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/*
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* check for more results |
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*/ |
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results = fcinfo->flinfo->fn_extra; |
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results->tup_num++; |
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ntuples = PQntuples(results->res); |
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if (results->tup_num < ntuples) { |
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/*
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* fetch them if available |
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*/ |
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rsi = (ReturnSetInfo *)fcinfo->resultinfo; |
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rsi->isDone = ExprMultipleResult; |
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PG_RETURN_POINTER(results); |
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} else { |
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/*
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* or if no more, clean things up |
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*/ |
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results = fcinfo->flinfo->fn_extra; |
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PQclear(results->res); |
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rsi = (ReturnSetInfo *)fcinfo->resultinfo; |
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rsi->isDone = ExprEndResult ; |
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PG_RETURN_NULL(); |
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} |
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} |
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PG_RETURN_NULL(); |
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} |
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/*
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* dblink_tok |
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* parse dblink output string |
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* return fldnum item (0 based) |
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* based on provided field separator |
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*/ |
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PG_FUNCTION_INFO_V1(dblink_tok); |
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Datum |
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dblink_tok(PG_FUNCTION_ARGS) |
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{ |
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dblink_results *results; |
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int fldnum; |
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text *result_text; |
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char *result; |
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int nfields = 0; |
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int text_len = 0; |
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if (PG_ARGISNULL(0) || PG_ARGISNULL(1)) { |
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elog(ERROR, "dblink: NULL arguments are not permitted"); |
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} |
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results = (dblink_results *) PG_GETARG_POINTER(0); |
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if (results == NULL) { |
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elog(ERROR, "dblink: function called with invalid result pointer"); |
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} |
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fldnum = PG_GETARG_INT32(1); |
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if (fldnum < 0) { |
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elog(ERROR, "dblink: field number < 0 not permitted"); |
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} |
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nfields = PQnfields(results->res); |
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if (fldnum > (nfields - 1)) { |
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elog(ERROR, "dblink: field number %d does not exist", fldnum); |
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} |
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text_len = PQgetlength(results->res, results->tup_num, fldnum); |
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|
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result = (char *) palloc(text_len + 1); |
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|
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if (result != NULL) { |
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strcpy(result, PQgetvalue(results->res, results->tup_num, fldnum)); |
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strcat(result, "\0"); |
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} else { |
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elog(ERROR, "dblink: insufficient memory" ); |
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} |
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result_text = DatumGetTextP(DirectFunctionCall1(textin, CStringGetDatum(result))); |
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|
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PG_RETURN_TEXT_P(result_text); |
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} |
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/*
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* internal functions |
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*/ |
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/*
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* init_dblink_results |
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* - create an empty dblink_results data structure |
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*/ |
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dblink_results * |
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init_dblink_results(MemoryContext fn_mcxt) |
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{ |
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MemoryContext oldcontext; |
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dblink_results *retval; |
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|
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oldcontext = MemoryContextSwitchTo(fn_mcxt); |
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|
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retval = (dblink_results *) palloc(sizeof(dblink_results)); |
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MemSet(retval, 0, sizeof(dblink_results)); |
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|
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retval->tup_num = -1; |
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retval->res = NULL; |
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|
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MemoryContextSwitchTo(oldcontext); |
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|
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return retval; |
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} |
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@ -0,0 +1,70 @@ |
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/*
|
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* dblink.h |
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* |
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* Functions returning results from a remote database |
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* |
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* Copyright (c) Joseph Conway <joe.conway@mail.com>, 2001; |
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*
|
||||
* Permission to use, copy, modify, and distribute this software and its |
||||
* documentation for any purpose, without fee, and without a written agreement |
||||
* is hereby granted, provided that the above copyright notice and this |
||||
* paragraph and the following two paragraphs appear in all copies. |
||||
*
|
||||
* IN NO EVENT SHALL THE AUTHOR OR DISTRIBUTORS BE LIABLE TO ANY PARTY FOR |
||||
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING |
||||
* LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS |
||||
* DOCUMENTATION, EVEN IF THE AUTHOR OR DISTRIBUTORS HAVE BEEN ADVISED OF THE |
||||
* POSSIBILITY OF SUCH DAMAGE. |
||||
*
|
||||
* THE AUTHOR AND DISTRIBUTORS SPECIFICALLY DISCLAIMS ANY WARRANTIES, |
||||
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY |
||||
* AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS |
||||
* ON AN "AS IS" BASIS, AND THE AUTHOR AND DISTRIBUTORS HAS NO OBLIGATIONS TO |
||||
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. |
||||
* |
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*/ |
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|
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#ifndef DBLINK_H |
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#define DBLINK_H |
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|
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#include <string.h> |
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#include "postgres.h" |
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#include "libpq-fe.h" |
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#include "libpq-int.h" |
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#include "fmgr.h" |
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#include "access/tupdesc.h" |
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#include "executor/executor.h" |
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#include "nodes/nodes.h" |
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#include "nodes/execnodes.h" |
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#include "utils/builtins.h" |
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|
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/*
|
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* This struct holds the results of the remote query. |
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* Use fn_extra to hold a pointer to it across calls |
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*/ |
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typedef struct |
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{ |
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/*
|
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* last tuple number accessed |
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*/ |
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int tup_num; |
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|
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/*
|
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* the actual query results |
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*/ |
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PGresult *res; |
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|
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} dblink_results; |
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|
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/*
|
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* External declarations |
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*/ |
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extern Datum dblink(PG_FUNCTION_ARGS); |
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extern Datum dblink_tok(PG_FUNCTION_ARGS); |
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|
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/*
|
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* Internal declarations |
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*/ |
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dblink_results *init_dblink_results(MemoryContext fn_mcxt); |
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|
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#endif /* DBLINK_H */ |
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@ -0,0 +1,5 @@ |
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CREATE FUNCTION dblink (text,text) RETURNS setof int |
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AS 'MODULE_PATHNAME','dblink' LANGUAGE 'c'; |
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|
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CREATE FUNCTION dblink_tok (int,int) RETURNS text |
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AS 'MODULE_PATHNAME','dblink_tok' LANGUAGE 'c'; |
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