I am trying to execute the following dynamic sql, but I could not figure out how to do it:
DROP FUNCTION f_mycross(text, text);
EXECUTE ('CREATE OR REPLACE FUNCTION f_mycross(text, text)
RETURNS TABLE ("registration_id" integer, '
|| (SELECT string_agg(DISTINCT pivot_headers, ',' order by pivot_headers)
FROM (SELECT DISTINCT '"' || qid::text || '" text' AS pivot_headers
FROM answers) x)
|| ') AS ''$libdir/tablefunc'',''crosstab_hash'' LANGUAGE C STABLE STRICT;')
I am relatively new to PostgreSQL.
Like a_horse commented, EXECUTE is not an SQL command. It's a PL/pgSQL command and can only be used in a function body or DO statement using this procedural language. Like:
DROP FUNCTION IF EXISTS f_mycross(text, text);
DO
$do$
BEGIN
EXECUTE (
SELECT 'CREATE OR REPLACE FUNCTION f_mycross(text, text)
RETURNS TABLE (registration_id integer, '
|| string_agg(pivot_header || ' text', ', ')
|| $$) AS '$libdir/tablefunc', 'crosstab_hash' LANGUAGE C STABLE STRICT$$
FROM (SELECT DISTINCT quote_ident(qid::text) AS pivot_header FROM answers ORDER BY 1) x
);
END
$do$; -- LANGUAGE plpgsql is the default
I added some improvements and simplified the nested SELECT query.
Major points
Add IF EXISTS to DROP FUNCTION unless you are certain the function exists or you want to raise an exception if it does not.
DISTINCT in the subquery is enough, no need for another DISTINCT in the outer SELECT.
Use quote_ident() to automatically double-quote identifiers where necessary.
No parentheses required around the string we feed to EXECUTE.
Simpler nested quoting with $-quotes.
Insert text with single quotes in PostgreSQL
We can apply ORDER BY in the subquery, which is typically much faster than adding ORDER BY in the outer aggregate function.
Related
May I know on how to call an array in stored procedure? I tried to enclosed it with a bracket to put the column_name that need to be insert in the new table.
CREATE OR REPLACE PROCEDURE data_versioning_nonull(new_table_name VARCHAR(100),column_name VARCHAR(100)[], current_table_name VARCHAR(100))
language plpgsql
as $$
BEGIN
EXECUTE ('CREATE TABLE ' || quote_ident(new_table_name) || ' AS SELECT ' || quote_ident(column_name) || ' FROM ' || quote_ident(current_table_name));
END $$;
CALL data_versioning_nonull('sales_2019_sample', ['orderid', 'product', 'address'], 'sales_2019');
Using execute format() lets you replace all the quote_ident() with %I placeholders in a single text instead of a series of concatenated snippets. %1$I lets you re-use the first argument.
It's best if you use ARRAY['a','b','c']::VARCHAR(100)[] to explicitly make it an array of your desired type. '{"a","b","c"}'::VARCHAR(100)[] works too.
You'll need to convert the array into a list of columns some other way, because when cast to text, it'll get curly braces which are not allowed in the column list syntax. Demo
It's not a good practice to introduce random limitations - PostgreSQL doesn't limit identifier lengths to 100 characters, so you don't have to either. The default limit is 63 bytes, so you can go way, way longer than 100 characters (demo). You can switch that data type to a regular text. Interestingly, exceeding specified varchar length would just convert it to unlimited varchar, making it just syntax noise.
DBFiddle online demo
CREATE TABLE sales_2019(orderid INT,product INT,address INT);
CREATE OR REPLACE PROCEDURE data_versioning_nonull(
new_table_name TEXT,
column_names TEXT[],
current_table_name TEXT)
LANGUAGE plpgsql AS $$
DECLARE
list_of_columns_as_quoted_identifiers TEXT;
BEGIN
SELECT string_agg(quote_ident(name),',')
INTO list_of_columns_as_quoted_identifiers
FROM unnest(column_names) name;
EXECUTE format('CREATE TABLE %1$I.%2$I AS SELECT %3$s FROM %1$I.%4$I',
current_schema(),
new_table_name,
list_of_columns_as_quoted_identifiers,
current_table_name);
END $$;
CALL data_versioning_nonull(
'sales_2019_sample',
ARRAY['orderid', 'product', 'address']::text[],
'sales_2019');
Schema awareness: currently the procedure creates the new table in the default schema, based on a table in that same default schema - above I made it explicit, but that's what it would do without the current_schema() calls anyway. You could add new_table_schema and current_table_schema parameters and if most of the time you don't expect them to be used, you can hide them behind procedure overloads for convenience, using current_schema() to keep the implicit behaviour. Demo
First, change your stored procedure to convert selected columns from array to csv like this.
CREATE OR REPLACE PROCEDURE data_versioning_nonull(new_table_name VARCHAR(100),column_name VARCHAR(100)[], current_table_name VARCHAR(100))
language plpgsql
as $$
BEGIN
EXECUTE ('CREATE TABLE ' || quote_ident(new_table_name) || ' AS SELECT ' || array_to_string(column_name, ',') || ' FROM ' || quote_ident(current_table_name));
END $$;
Then call it as:
CALL data_versioning_nonull('sales_2019_sample', '{"orderid", "product", "address"}', 'sales_2019');
I have a database with multiple identical schemas. There is a number of tables all named 'tran_...' in each schema. I want to loop through all 'tran_' tables in all schemas and pull out records that fall within a specific date range. This is the code I have so far:
CREATE OR REPLACE FUNCTION public."configChanges"(starttime timestamp, endtime timestamp)
RETURNS SETOF character varying AS
$BODY$DECLARE
tbl_row RECORD;
tbl_name VARCHAR(50);
tran_row RECORD;
out_record VARCHAR(200);
BEGIN
FOR tbl_row IN
SELECT * FROM pg_tables WHERE schemaname LIKE 'ivr%' AND tablename LIKE 'tran_%'
LOOP
tbl_name := tbl_row.schemaname || '.' || tbl_row.tablename;
FOR tran_row IN
SELECT * FROM tbl_name
WHERE ch_edit_date >= starttime AND ch_edit_date <= endtime
LOOP
out_record := tbl_name || ' ' || tran_row.ch_field_name;
RETURN NEXT out_record;
END LOOP;
END LOOP;
RETURN;
END;
$BODY$
LANGUAGE plpgsql;
When I attempt to run this, I get:
ERROR: relation "tbl_name" does not exist
LINE 1: SELECT * FROM tbl_name WHERE ch_edit_date >= starttime AND c...
#Pavel already provided a fix for your basic error.
However, since your tbl_name is actually schema-qualified (two separate identifiers in : schema.table), it cannot be escaped as a whole with %I in format(). You have to escape each identifier individually.
Aside from that, I suggest a different approach. The outer loop is necessary, but the inner loop can be replaced with a simpler and more efficient set-based approach:
CREATE OR REPLACE FUNCTION public.config_changes(_start timestamp, _end timestamp)
RETURNS SETOF text AS
$func$
DECLARE
_tbl text;
BEGIN
FOR _tbl IN
SELECT quote_ident(schemaname) || '.' || quote_ident(tablename)
FROM pg_tables
WHERE schemaname LIKE 'ivr%'
AND tablename LIKE 'tran_%'
LOOP
RETURN QUERY EXECUTE format (
$$
SELECT %1$L || ' ' || ch_field_name
FROM %1$s
WHERE ch_edit_date BETWEEN $1 AND $2
$$, _tbl
)
USING _start, _end;
END LOOP;
RETURN;
END
$func$ LANGUAGE plpgsql;
You have to use dynamic SQL to parametrize identifiers (or code), like #Pavel already told you. With RETURN QUERY EXECUTE you can return the result of a dynamic query directly. Examples:
Return SETOF rows from PostgreSQL function
Refactor a PL/pgSQL function to return the output of various SELECT queries
Remember that identifiers have to be treated as unsafe user input in dynamic SQL and must always be sanitized to avoid syntax errors and SQL injection:
Table name as a PostgreSQL function parameter
Note how I escape table and schema separately:
quote_ident(schemaname) || '.' || quote_ident(tablename)
Consequently I just use %s to insert the already escaped table name in the later query. And %L to escape it a string literal for output.
I like to prepend parameter and variable names with _ to avoid naming conflicts with column names. No other special meaning.
There is a slight difference compared to your original function. This one returns an escaped identifier (double-quoted only where necessary) as table name, e.g.:
"WeIRD name"
instead of
WeIRD name
Much simpler yet
If possible, use inheritance to obviate the need for above function altogether. Complete example:
Select (retrieve) all records from multiple schemas using Postgres
You cannot use a plpgsql variable as SQL table name or SQL column name. In this case you have to use dynamic SQL:
FOR tran_row IN
EXECUTE format('SELECT * FROM %I
WHERE ch_edit_date >= starttime AND ch_edit_date <= endtime', tbl_name)
LOOP
out_record := tbl_name || ' ' || tran_row.ch_field_name;
RETURN NEXT out_record;
END LOOP;
In continuation to a previous case (a solution by #Erwin Brandstetter), in which a dynamic SELECT query that uses a 'prepare' statement was created and then was executed by calling it, as below:
--the function for making the prepare statement:
CREATE OR REPLACE FUNCTION f_prep_query (_tbl regclass, _prefix text)
RETURNS void AS
$func$
DECLARE
_prep_qry text := (
SELECT 'PREPARE stmt_dyn AS SELECT '
|| string_agg(quote_ident(attname), ',' ORDER BY attname)
|| ' FROM ' || _tbl
FROM pg_attribute
WHERE attrelid = _tbl
AND attname LIKE _prefix || '%'
AND attnum > 0
AND NOT attisdropped
);
BEGIN
EXECUTE _prep_qry;
EXCEPTION WHEN duplicate_prepared_statement THEN
DEALLOCATE stmt_dyn;
EXECUTE _prep_qry;
END
$func$ LANGUAGE plpgsql;
--the calling:
BEGIN; -- optional
SELECT f_prep_query('dkj_p_k27ac'::regclass, 'enri'::text);
EXECUTE stmt_dyn;
I would like to ask the following:
The desired output that we get from the indicated procedure is outputted into the DataOutput.
I would like to find a way to store the data into a new table in the db.
Generally, if you just want to write to a table, don't use a prepared SELECT statement (or a cursor). That's very inefficient for the purpose.
Write to the table directly like explained in the previous answer:
Saving the output of a dynamic query that uses refcursor into a table
The complete INSERT could be the prepared statement. But not CREATE TABLE AS. Per documentation:
Any SELECT, INSERT, UPDATE, DELETE, or VALUES statement.
I have created the following stored procedure, which basically receives a name of table, and a prefix. The function then finds all columns that share this prefix and returns as an output a 'select' query command ('myoneliner').
as follows:
CREATE OR REPLACE FUNCTION mytext (mytable text, myprefix text)
RETURNS text AS $myoneliner$
declare
myoneliner text;
BEGIN
SELECT 'SELECT ' || substr(cols,2,length(cols)-2) ||' FROM '||mytable
INTO myoneliner
FROM (
SELECT array(
SELECT DISTINCT quote_ident(column_name::text)
FROM information_schema.columns
WHERE table_name = mytable
AND column_name LIKE myprefix||'%'
order by quote_ident
)::text cols
) sub;
RETURN myoneliner;
END;
$myoneliner$ LANGUAGE plpgsql;
Call:
select mytext('dkj_p_k27ac','enri');
As a result of running this stored procedure and the 'select' that is following it, I get the following output at the Data Output window (all within one cell, named "mytext text"):
'SELECT enrich_d_dkj_p_k27ac,enrich_lr_dkj_p_k27ac,enrich_r_dkj_p_k27ac
FROM dkj_p_k27ac'
I would like to basically be able to take the output command line that I received as an output and execute it. In other words, I would like to be able and execute the output of my stored procedure.
How can I do so?
I tried the following:
CREATE OR REPLACE FUNCTION mytext (mytable text, myprefix text)
RETURNS SETOF RECORD AS $$
declare
smalltext text;
myoneliner text;
BEGIN
SELECT 'SELECT ' || substr(cols,2,length(cols)-2) ||' FROM '||mytable
INTO myoneliner
FROM (
SELECT array(
SELECT DISTINCT quote_ident(column_name::text)
FROM information_schema.columns
WHERE table_name = mytable
AND column_name LIKE myprefix||'%'
order by quote_ident
)::text cols
) sub;
smalltext=lower(myoneliner);
raise notice '%','my additional text '||smalltext;
RETURN QUERY EXECUTE smalltext;
END;
$$ LANGUAGE plpgsql;
Call function:
SELECT * from mytext('dkj_p_k27ac','enri');
But I'm getting the following error message, could you please advise what should I change in order for it to execute?:
ERROR: a column definition list is required for functions returning "record"
LINE 26: SELECT * from mytext('dkj_p_k27ac','enri');
********** Error **********
ERROR: a column definition list is required for functions returning "record"
SQL state: 42601
Character: 728
Your first problem was solved by using dynamic SQL with EXECUTE like Craig advised.
But the rabbit hole goes deeper:
CREATE OR REPLACE FUNCTION myresult(mytable text, myprefix text)
RETURNS SETOF RECORD AS
$func$
DECLARE
smalltext text;
myoneliner text;
BEGIN
SELECT INTO myoneliner
'SELECT '
|| string_agg(quote_ident(column_name::text), ',' ORDER BY column_name)
|| ' FROM ' || quote_ident(mytable)
FROM information_schema.columns
WHERE table_name = mytable
AND column_name LIKE myprefix||'%'
AND table_schema = 'public'; -- schema name; might be another param
smalltext := lower(myoneliner); -- nonsense
RAISE NOTICE 'My additional text: %', myoneliner;
RETURN QUERY EXECUTE myoneliner;
END
$func$ LANGUAGE plpgsql;
Major points
Don't cast the whole statement to lower case. Column names might be double-quoted with upper case letters, which are case-sensitive in this case (no pun intended).
You don't need DISTINCT in the query on information_schema.columns. Column names are unique per table.
You do need to specify the schema, though (or use another way to single out one schema), or you might be mixing column names from multiple tables of the same name in multiple schemas, resulting in nonsense.
You must sanitize all identifiers in dynamic code - including table names: quote_ident(mytable). Be aware that your text parameter to the function is case sensitive! The query on information_schema.columns requires that, too.
I untangled your whole construct to build the list of column names with string_agg() instead of the array constructor. Related answer:
Update multiple columns that start with a specific string
The assignment operator in plpgsql is :=.
Simplified syntax of RAISE NOTICE.
Core problem impossible to solve
All of this still doesn't solve your main problem: SQL demands a definition of the columns to be returned. You can circumvent this by returning anonymous records like you tried. But that's just postponing the inevitable. Now you have to provide a column definition list at call time, just like your error message tells you. But you just don't know which columns are going to be returned. Catch 22.
Your call would work like this:
SELECT *
FROM myresult('dkj_p_k27ac','enri') AS f (
enrich_d_dkj_p_k27ac text -- replace with actual column types
, enrich_lr_dkj_p_k27ac text
, enrich_r_dkj_p_k27ac text);
But you don't know number, names (optional) and data types of returned columns, not at creation time of the function and not even at call time. It's impossible to do exactly that in a single call. You need two separate queries to the database.
You could return all columns of any given table dynamically with a function using polymorphic types, because there is a well defined type for the whole table. Last chapter of this related answer:
Refactor a PL/pgSQL function to return the output of various SELECT queries
I'm trying to write a function in PL/PgSQL that have to work with a table it receives as a parameter.
I use EXECUTE..INTO..USING statements within the function definition to build dynamic queries (it's the only way I know to do this) but ... I encountered a problem with RECORD data types.
Let's consider the follow (extremely simplified) example.
-- A table with some values.
DROP TABLE IF EXISTS table1;
CREATE TABLE table1 (
code INT,
descr TEXT
);
INSERT INTO table1 VALUES ('1','a');
INSERT INTO table1 VALUES ('2','b');
-- The function code.
DROP FUNCTION IF EXISTS foo (TEXT);
CREATE FUNCTION foo (tbl_name TEXT) RETURNS VOID AS $$
DECLARE
r RECORD;
d TEXT;
BEGIN
FOR r IN
EXECUTE 'SELECT * FROM ' || tbl_name
LOOP
--SELECT r.descr INTO d; --IT WORK
EXECUTE 'SELECT ($1)' || '.descr' INTO d USING r; --IT DOES NOT WORK
RAISE NOTICE '%', d;
END LOOP;
END;
$$ LANGUAGE plpgsql STRICT;
-- Call foo function on table1
SELECT foo('table1');
It output the following error:
ERROR: could not identify column "descr" in record data type
although the syntax I used seems valid to me. I can't use the static select (commented in the example) because I want to dinamically refer the columns names.
So..someone know what's wrong with the above code?
It's true. You cannot to use type record outside PL/pgSQL space.
RECORD value is valid only in plpgsql.
you can do
EXECUTE 'SELECT $1.descr' INTO d USING r::text::xx;
$1 should be inside the || ,like || $1 || and give spaces properly then it will work.
BEGIN
EXECUTE ' delete from ' || quote_ident($1) || ' where condition ';
END;