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)