DBLINK_BUILD_SQL_UPDATE(3) PostgreSQL 9.2.7 Documentation DBLINK_BUILD_SQL_UPDATE(3)
NAME
dblink_build_sql_update - builds an UPDATE statement using a local tuple, replacing the primary key field values with alternative supplied
values
SYNOPSIS
dblink_build_sql_update(text relname,
int2vector primary_key_attnums,
integer num_primary_key_atts,
text[] src_pk_att_vals_array,
text[] tgt_pk_att_vals_array) returns text
DESCRIPTION
dblink_build_sql_update can be useful in doing selective replication of a local table to a remote database. It selects a row from the local
table based on primary key, and then builds a SQL UPDATE command that will duplicate that row, but with the primary key values replaced by
the values in the last argument. (To make an exact copy of the row, just specify the same values for the last two arguments.) The UPDATE
command always assigns all fields of the row -- the main difference between this and dblink_build_sql_insert is that it's assumed that the
target row already exists in the remote table.
ARGUMENTS
relname
Name of a local relation, for example foo or myschema.mytab. Include double quotes if the name is mixed-case or contains special
characters, for example "FooBar"; without quotes, the string will be folded to lower case.
primary_key_attnums
Attribute numbers (1-based) of the primary key fields, for example 1 2.
num_primary_key_atts
The number of primary key fields.
src_pk_att_vals_array
Values of the primary key fields to be used to look up the local tuple. Each field is represented in text form. An error is thrown if
there is no local row with these primary key values.
tgt_pk_att_vals_array
Values of the primary key fields to be placed in the resulting UPDATE command. Each field is represented in text form.
RETURN VALUE
Returns the requested SQL statement as text.
NOTES
As of PostgreSQL 9.0, the attribute numbers in primary_key_attnums are interpreted as logical column numbers, corresponding to the column's
position in SELECT * FROM relname. Previous versions interpreted the numbers as physical column positions. There is a difference if any
column(s) to the left of the indicated column have been dropped during the lifetime of the table.
EXAMPLES
SELECT dblink_build_sql_update('foo', '1 2', 2, '{"1", "a"}', '{"1", "b"}');
dblink_build_sql_update
-------------------------------------------------------------
UPDATE foo SET f1='1',f2='b',f3='1' WHERE f1='1' AND f2='b'
(1 row)
PostgreSQL 9.2.7 2014-02-17 DBLINK_BUILD_SQL_UPDATE(3)