1DBLINK_BUILD_SQL_UPDATE(3)PostgreSQL 15.4 DocumentatioDnBLINK_BUILD_SQL_UPDATE(3)
2
6 dblink_build_sql_update - builds an UPDATE statement using a local
7 tuple, replacing the primary key field values with alternative supplied
8 values
9
11 dblink_build_sql_update(text relname,
12 int2vector primary_key_attnums,
13 integer num_primary_key_atts,
14 text[] src_pk_att_vals_array,
15 text[] tgt_pk_att_vals_array) returns text
16
18 dblink_build_sql_update can be useful in doing selective replication of
19 a local table to a remote database. It selects a row from the local
20 table based on primary key, and then builds an SQL UPDATE command that
21 will duplicate that row, but with the primary key values replaced by
22 the values in the last argument. (To make an exact copy of the row,
23 just specify the same values for the last two arguments.) The UPDATE
24 command always assigns all fields of the row — the main difference
25 between this and dblink_build_sql_insert is that it's assumed that the
26 target row already exists in the remote table.
27
29 relname
30 Name of a local relation, for example foo or myschema.mytab.
31 Include double quotes if the name is mixed-case or contains special
32 characters, for example "FooBar"; without quotes, the string will
33 be folded to lower case.
34 primary_key_attnums
36 Attribute numbers (1-based) of the primary key fields, for example
37 1 2.
38 num_primary_key_atts
40 The number of primary key fields.
41 src_pk_att_vals_array
43 Values of the primary key fields to be used to look up the local
44 tuple. Each field is represented in text form. An error is thrown
45 if there is no local row with these primary key values.
46 tgt_pk_att_vals_array
48 Values of the primary key fields to be placed in the resulting
49 UPDATE command. Each field is represented in text form.
50
52 Returns the requested SQL statement as text.
53
55 As of PostgreSQL 9.0, the attribute numbers in primary_key_attnums are
56 interpreted as logical column numbers, corresponding to the column's
57 position in SELECT * FROM relname. Previous versions interpreted the
58 numbers as physical column positions. There is a difference if any
59 column(s) to the left of the indicated column have been dropped during
60 the lifetime of the table.
61
63 SELECT dblink_build_sql_update('foo', '1 2', 2, '{"1", "a"}', '{"1", "b"}');
64 dblink_build_sql_update
65 -------------------------------------------------------------
66 UPDATE foo SET f1='1',f2='b',f3='1' WHERE f1='1' AND f2='b'
67 (1 row)
68PostgreSQL 15.4 2023 DBLINK_BUILD_SQL_UPDATE(3)