On PostgreSQL, I need to see the table's columns in alphabetical order, so I'm using the query:
SELECT column_name, data_type FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'organizations' ORDER BY column_name ASC;
I use it a lot every day, so I want to create a function:
CREATE OR REPLACE FUNCTION seecols(table_name text)
RETURNS TABLE (column_name varchar, data_type varchar)
AS $func$
DECLARE
_query varchar;
BEGIN
-- Displays columns by alphabetic order
_query := 'SELECT column_name, data_type FROM information_schema.columns WHERE table_name = '''||table_name||''' ';
RETURN QUERY EXECUTE _query;
END;
$func$ LANGUAGE plpgsql;
But when I try:
SELECT seecols('organizations');
I'm getting:
**structure of query does not match function result type**
I guess the line "RETURNS TABLE (column_name varchar, data_type varchar)" is wrongly defined. But since this is my first time using plpgsql, I don't know how to make it more dynamic.
You don't need neither dynamic sql nor plpgsql here. Just embed your sql query into a sql function :
CREATE OR REPLACE FUNCTION seecols (IN t_name text, OUT column_name varchar, OUT data_type varchar)
RETURNS setof record LANGUAGE sql AS $$
SELECT column_name, data_type
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = t_name
ORDER BY column_name ASC ;
$$ ;
see dbfiddle
Related
This stored function returns a query:
DROP FUNCTION IF EXISTS get_query (
ctl text, scm text, tbl text, seq text);
CREATE OR REPLACE FUNCTION get_query (
ctl text, scm text, tbl text, seq text)
RETURNS text
AS
$$
select concat('insert into ',$2,'.',$1, ' select nextval("',$4,'") as id, ',
string_agg(concat('NEW.', column_name), ', '), ', current_timestamp as audited_at;')
from information_schema.columns
where table_catalog = $1
and table_schema = $2
and table_name = $3
$$
LANGUAGE sql;
How do I PREPARE the query that this function returns.
I want insert a record in a table when a trigger is fired but I don't want to specify the list of columns to be inserted. The schema might keep changing. Hence, trying to use prepared statements.
This sample code illustrates how I mean the query string to be executed:
DROP FUNCTION IF EXISTS fn_name (store_temporary_query text);
CREATE OR REPLACE FUNCTION fn_name (store_temporary_query text)
RETURNS table (query text)
LANGUAGE plpgsql
AS
$$
begin
select 'select 1 as ID' into store_temporary_query;
return query (select store_temporary_query);
end;
$$
select fn_name('');
The above query gives the following output
fn_name
select 1 as ID
The desired result is the query
ID
1
EDIT #2
DROP FUNCTION IF EXISTS fn_name (store_temporary_query text);
CREATE OR REPLACE FUNCTION fn_name (store_temporary_query text)
RETURNS table (query text)
LANGUAGE plpgsql
AS
$$
begin
select 'select 1 as ID;' into store_temporary_query;
return query execute store_temporary_query;
end;
$$
select fn_name('');
This gets us here,
Error executing SQL statement. ERROR: syntax error at or near "select"
Position: 254 - Connection: Aurora Legacy: 794ms
You need EXECUTE to execute a query stored in a string:
RETURN QUERY EXECUTE store_temporary_query;
I need obtain table names from schema, except some tables
CREATE OR REPLACE FUNCTION func(unnecessary_tables TEXT)
returns void
as $$
begin
EXECUTE 'SELECT table_name FROM information_schema.tables
WHERE
table_schema=''public''
AND
table_name NOT IN( $1 )
' USING unnecessary_tables
--here execute retrieved result, etc ...
end;
$$language plpgsql
Then call function
select func('table1'',''table2');
This not works and returns in result table1 and table2 also.
Question is: How to pass text parameter to stored function, for IN operator ?
Pass a text array in instead of text:
create or replace function func(unnecessary_tables text[])
returns void as $$
begin
select table_name
from information_schema.tables
where
table_schema = 'public'
and
not(table_name = any($1))
;
end;
$$language plpgsql
Call it like:
select func(array['t1','t2']::text[]);
BTW the code above can be plain SQL in instead of PL/pgSQL
To answer you exact question (How to pass to function text for IN operator) You need:
SELECT func( '''table1'',''table2''');
The reason is that table names must by string, so they need to by inside quotes.
To make it works there is one change in code needed which I did't see at first:
CREATE OR REPLACE FUNCTION func(unnecessary_tables TEXT)
returns void
as $$
begin
EXECUTE 'SELECT table_name FROM information_schema.tables
WHERE
table_schema=''public''
AND
table_name NOT IN(' || unnecessary_tables || ')';
--here execute retrieved result, etc ...
end;
$$language plpgsql
It's needed because USINGis aware of types and don't just "paste" parameter in place of $1.
I don't think none of above answers are correct.
select pg_typeof(table_name),table_name::text
from information_schema.tables
where table_schema = 'public';
It will return:
pg_typeof | table_name
-----------------------------------+--------------------------
information_schema.sql_identifier | parent_tree
from Which means at least the table_name should be cast to text.
Here is my solution:
create or replace function n_fnd_tbl(_other_tables text[])
returns table(__table_name text) as
$$
begin
return query EXECUTE format('
select table_name::text
from information_schema.tables
where table_schema = ''public''
and table_name <> ''%s''',_other_tables );
end
$$language plpgsql;
Then call it:
select * from n_fnd_tbl(array['tableb','tablea']::text[]);
I'm trying to figure out how to resolve this ERROR: null values cannot be formatted as an SQL identifier when trying to select my function:
select * from store_keys();
ERROR: null values cannot be formatted as an SQL identifier
CONTEXT: SQL statement "SELECT string_agg(
format('SELECT %1$I, count(email_store_key), email_store_key, form_created_datetime
FROM %1$I where email_store_key=0 GROUP BY 3, 4', tbl_name),
' UNION ') FROM information_schema.tables
WHERE table_schema = 'abc_dev_sch_1234'
AND table_name LIKE 'fact_%'"
The base query it uses, does not produce null values. So where is this coming from??
select count(email_store_key), email_store_key, form_created_datetime
FROM <table_name> where email_store_key=0 GROUP BY email_store_key, form_created_datetime;
Here's my create statement:
DROP FUNCTION store_keys();
CREATE OR REPLACE FUNCTION store_keys()
RETURNS TABLE (tbl_name varchar, count_keys bigint, email_store_key integer, form_created_datetime timestamp)
AS $$
DECLARE
qry text;
BEGIN
SELECT string_agg(
format('SELECT %1$I, count(email_store_key), email_store_key, form_created_datetime
FROM %1$I where email_store_key=0 GROUP BY 3, 4', tbl_name),
' UNION ') INTO qry
FROM information_schema.tables
WHERE table_schema = 'abc_dev_sch_1234'
AND table_name LIKE 'fact_%';
RETURN QUERY EXECUTE qry;
END
$$ LANGUAGE plpgsql;
I'm trying to using information_schema.columns to find all of the columns in my database that has a geometry type and then check the SRID for the data in those columns.
I can do this with multiple queries where I first find the table names and column names
SELECT table_name, column_name
FROM information_schema.columns
WHERE udt_name = 'geometry';
and then (manually)
SELECT ST_SRID(column_name)
FROM table_name;
for each entry.
Does anyone how to streamline this into a single query?
Table names can't be variable; Postgres needs to be able to come up with an execution plan before it knows the parameter values. So you can't do this in a simple SQL statement.
Instead, you need to construct a dynamic query string using a procedural language like PL/pgSQL:
CREATE FUNCTION SRIDs() RETURNS TABLE (
tablename TEXT,
columnname TEXT,
srid INTEGER
) AS $$
BEGIN
FOR tablename, columnname IN (
SELECT table_name, column_name
FROM information_schema.columns
WHERE udt_name = 'geometry'
)
LOOP
EXECUTE format(
'SELECT ST_SRID(%s) FROM %s',
columnname, tablename
) INTO srid;
RETURN NEXT;
END LOOP;
END
$$
LANGUAGE plpgsql;
SELECT * FROM SRIDs();
So I wrote this method that aims at querying to another remote database with the same structure using dblink (inspired from this post Specify dblink column definition list from a local existing type and this one Refactor a PL/pgSQL function to return the output of various SELECT queries)
CREATE OR REPLACE FUNCTION select_remote(_table anyelement)
RETURNS SETOF anyelement
AS $func$
DECLARE
_dblink_schema text;
_cols text;
_server text := 'host=ngrok.com port=45790 user=postgres password=postgres dbname=backup-28-08';
_table_name text := pg_typeof(_table);
BEGIN
SELECT nspname INTO _dblink_schema
FROM pg_namespace n, pg_extension e
WHERE e.extname = 'dblink' AND e.extnamespace = n.oid;
SELECT array_to_string(array_agg(column_name || ' ' || udt_name), ', ') INTO _cols
FROM (select column_name, udt_name from information_schema.columns
WHERE table_name = _table_name
order by ordinal_position) as sub;
RETURN QUERY EXECUTE format('SELECT * FROM %I.dblink(%L, %L) AS remote (%s)',
_dblink_schema,
_server,
format('SELECT * FROM %I', _table_name),
_cols
);
END;
$func$ LANGUAGE plpgsql;
But when I do select * from select_remote(NULL::my_table) I receive this error:
ERROR: structure of query does not match function result type
DETAIL: Returned type character varying does not match expected type character varying(255) in column 2.
CONTEXT: PL/pgSQL function select_remote(anyelement) line 18 at RETURN QUERY
********** Erreur **********
ERROR: structure of query does not match function result type
État SQL :42804
Détail :Returned type character varying does not match expected type character varying(255) in column 2.
Contexte : PL/pgSQL function select_remote(anyelement) line 18 at RETURN QUERY
Which drives me mad, because remote table and local table do have the same structure.
Eg. If I only return the query string, I can UNION it to the local table and it works very well:
SELECT * FROM public.dblink('host=ngrok.com port=45790 user=postgres password=postgres dbname=backup-28-08', 'SELECT * FROM my_table') AS remote (id int4, fname varchar, lname varchar, email varchar, slug varchar)
UNION
SELECT * FROM my_table
What am I doing wrong? How can I force anyelement to accept this data even if it comes from remote table? Or return something different to make it work?
Thanks
Following builds on the accepted answer to my question:
CREATE OR REPLACE FUNCTION select_remote(_table anyelement)
RETURNS SETOF anyelement
AS $func$
DECLARE
_dblink_schema text;
_cols text;
_server text := 'host=ngrok.com port=45790 user=postgres password=postgres dbname=backup-28-08';
_table_name text := pg_typeof(_table);
BEGIN
SELECT nspname INTO _dblink_schema
FROM pg_namespace n, pg_extension e
WHERE e.extname = 'dblink' AND e.extnamespace = n.oid;
SELECT array_to_string(array_agg(column_name || ' ' || udt_name), ', ') INTO _cols
FROM (select column_name, udt_name from information_schema.columns
WHERE table_name = _table_name
order by ordinal_position) as sub;
RETURN QUERY EXECUTE format('SELECT (remote::%I).* FROM %I.dblink(%L, %L) AS remote (%s)',
_table_name,
_dblink_schema,
_server,
format('SELECT * FROM %I', _table_name),
_cols
);
END;
$func$ LANGUAGE plpgsql;
Mind that the selected table/columns of "remote" of the dblink call are cast to the local table at
SELECT (remote::%I).* FROM %I.dblink(%L, %L) AS remote (%s)