I've been trying to delete a tablespace if it exists in DB2 (Z/OS) if it exists. The purpose of this is to be able to have a script to create a new dev or replace an existing dev database.
I've been trying something like:
BEGIN
IF (exists (SELECT * FROM SYSIBM.SYSTABLESPACES WHERE TBSPACE = 'SGE')) THEN
DROP TABLESPACE "SGE";
END IF;
END #
But it doesn't seem to be taking the DROP (at least on Data Studio 4.1). Is there anything else I should be doing?
Thanks in advance
mustaccio was right on his comment. I left the code like this and it worked for me:
BEGIN
IF (exists (SELECT * FROM SYSIBM.SYSTABLESPACES WHERE TBSPACE = 'SGE')) THEN
EXECUTE IMMEDIATE 'DROP TABLESPACE "SGE"';
END IF;
END #
I can do the same for other objects as well such as schemas, etc. I only need to change the exists condition based on what I want to delete.
Related
Below is a great function to check the real count of all tables in PostgreSQL database. I found it here.
From my local test, it seems that the function returns the all result only after it finished all counting for 100 tables.
I am trying to make it more practical. If we could save the result of each table counting as soon as it finished with the table, then we can check the progress of all counting jobs instead of waiting for the end.
I think if I could UPDATE the result in this function immediately after finishing the first table, it will be great for my requirement.
Can you let me know how I can update the result into the table after this function finishes the counting of the first table?
CREATE FUNCTION rowcount_all(schema_name text default 'public')
RETURNS table(table_name text, cnt bigint) as
$$
declare
table_name text;
begin
for table_name in SELECT c.relname FROM pg_class c
JOIN pg_namespace s ON (c.relnamespace=s.oid)
WHERE c.relkind = 'r' AND s.nspname=schema_name
ORDER BY c.relname
LOOP
RETURN QUERY EXECUTE format('select count(*) from %I.%I',
table_name, schema_name, table_name);
END LOOP;
end
$$ language plpgsql;
-- Query
WITH rc(schema_name,tbl) AS (
select s.n,rowcount_all(s.n) from (values ('schema1'),('schema2')) as s(n)
)
SELECT schema_name,(tbl).* FROM rc;
Updated
I have decided to use a shell script to run the function below as a background process. The function would generate a processing log file so that I can check the current process.
I think your idea is good, but I also don't think it will work "out of the box" on PostgreSQL. I'm by no means the expert on this, but the way MVCC works on PostgreSQL, it's basically doing all of the DML in what can best be understood as temporary space, and then if and when everything works as expected it moves it all in at the end.
This has a lot of advantages, most notably that when someone is updating tables it doesn't prevent others from querying from those same tables.
If this were Oracle, I think you could accomplish this within the stored proc by using commit, but this isn't Oracle. And to be fair, Oracle doesn't allow truncates to be rolled back within a stored proc the way PostgreSQL does, so there are gives and takes.
Again, I'm not the expert, so if I've messed up a detail or two, feel free to correct me.
So, back to the solution. One way you COULD accomplish this is to set up your server as a remote server. Something like this would work:
CREATE SERVER pgprod
FOREIGN DATA WRAPPER dblink_fdw
OPTIONS (dbname 'postgres', host 'localhost', port '5432');
Assuming you have a table that stores the tables and counts:
create table table_counts (
table_name text not null,
record_count bigint,
constraint table_counts_pk primary key (table_name)
);
Were it not for your desire to see these results as they occur, something like this would work, for a single schema. It's easy enough to make this all schemas, so this is for illustration:
CREATE or replace FUNCTION rowcount_all(schema_name text)
returns void as
$$
declare
rowcount integer;
tablename text;
begin
for tablename in SELECT c.relname FROM pg_class c
JOIN pg_namespace s ON (c.relnamespace=s.oid)
WHERE c.relkind = 'r' AND s.nspname=schema_name
ORDER BY c.relname
LOOP
EXECUTE 'select count(*) from ' || schema_name || '.' || tablename into rowcount;
insert into table_counts values (schema_name || '.' || tablename, rowcount)
on conflict (table_name) do
update set record_count = rowcount;
END LOOP;
end
$$ language plpgsql;
(this presupposes 9.5 or greater -- if not, hand-roll your own upsert).
However, since you want real-time updates to the table, you could then put that same upsert into a dblink expression:
perform dblink_exec('pgprod', '
<< your upsert statement here >>
');
Of course the formatting of the SQL within the DBlink is now a little extra tricky, but the upside is once you nail it, you can run the function in the background and query the table while it's running to see the dynamic results.
I'd weigh that against the need to really have the information real-time.
This is a SQL learning exercise. I have a 'tbl' with a single integer field. There are no indices on this table. I have this function:
CREATE OR REPLACE FUNCTION rcs()
RETURNS VOID AS $$
DECLARE
c CURSOR FOR SELECT * FROM tbl ORDER BY sequence;
s INTEGER;
r RECORD;
BEGIN
s := 0;
OPEN c;
LOOP
FETCH c INTO r;
EXIT WHEN NOT FOUND;
RAISE NOTICE 'got it';
r.sequence = s;
s := s + 1;
RAISE NOTICE '%', r.sequence;
END LOOP;
CLOSE c;
END;
$$ language 'plpgsql'
This loads and runs cleanly and the RAISE statements suggest that the 'sequence' field gets updated to 0, 1 etc. in accordance with the ORDER BY.
However, when I SELECT the table afterwards, the pre-existing values (which happen to all be '6') did not change.
Is this something to do with transactions? I tried fiddling around with COMMIT, etc. to no avail.
This is a freshly installed Postgresql 9.4.4 running on a Linode with no hackery of config files or anything like that, from the 'psql' command line.
EDIT: maybe it's because 'r' isn't actually the DB table, it's some kind of temporary copy of it? If so, please clarify, hopefully what I'm trying to achieve here is obvious (and I know it may be a bit nonsensical, but surely it's possible without resorting to reading the set into Java, etc.)
The actual problem: your function does not contain an UPDATE statement so nothing gets written to disk. r.sequence = s; simply assigns a new value to a variable that is held in memory.
To fix this, you need something like:
UPDATE tbl
set sequence = s -- change the actual column in the table
WHERE current of c; -- for the current row of your cursor
If where current of doesn't work, you need to switch that to a "regular" where clause:
UPDATE tbl
set sequence = s
WHERE tbl.pk_column = r.pk_column; -- the current primary key value
But a much more efficient solution is to do this in a single statement:
update tbl
set sequence = tu.new_sequence
from (
select t.pk_column,
row_number() over (order by t.sequence) as new_sequence
from tbl t
) tu
where tbl.pk_column = tu.pk_column;
You need to replace the column name pk_column with the real primary key (or unique) column of your table.
I am new to PostgreSQL and I'm trying to create a trigger on update. I have two tables source and destination with same table structure. So I want the records to be updated on destination when there is an update on source. I tried the below trigger function:
Create FUNCTION ins_functiontest() RETURNS trigger AS '
BEGIN
IF tg_op = ''UPDATE'' THEN
INSERT INTO destination(id,name,tg_op)
VALUES (new.id,new.name, tg_op);
RETURN new;
END IF;
END
' LANGUAGE plpgsql;
Column 'id' is primary key on both tables so the above function fails as when there is an update on source as that record already exists on destination.
I tried to modify function to update rest of the columns in the table comparing the id fields on source and destination.
Update des
Set name = new.name,tg_op= update
From destination des join source src
ON des.id = src.id
Where des.id = src.id
But couldn't get the syntax correct. Any help would be most appreciated.
I'm using PostgreSQL 8.4.
I figured out solution for my problem, Below is the answer.
Create FUNCTION ins_functiontest() RETURNS trigger AS '
BEGIN
IF tg_op = ''UPDATE'' THEN
Update destination_table_name
SET
name = new.name,
Where id = new.id;
END IF;
END
' LANGUAGE plpgsql;
I did something similar for my log tables. But I duplicate the colums. 1 set for the new.* to catch insert and update and a set for the old.* also for update and delete. Then inserted a serials primary key, the time and idtransaction, txid_current(). The only bullet proof is the serial. The idtransaction depend from wich server works. If you change pc, and it can happen in the lifetime of a db, it will start again the counter. But cannot happen that two transactions with same id have same time. But can happen two transaction at the same time. Expecially if you have several users. connected
In my script I have to do a lot of selects to a joined table, so instead I decided to put this join into a temporal table.
First I thought:
1. Create table
2. Put the data from the join into a table
3. Drop the table
But then I thought, what if the script fails before I dropped the table?
So I decided to go with:
1. Drop the table
2. Create the table
3. Put the data from the join into a table
I don't really mind if the table is left there until the next time I run the script, so the second option works too.
But what if somebody had already dropped the table?
I saw some systems have a "drop if exists" but unfortunately not DB2. I would like to do something that won't make the script die when the drop table fails.
Ideas? On any of this? Thanks!
EDIT: I forgot to say this is in a PERL script!
The best way to do this is by using an annonymous block like in this code
You need to call the drop table in a dynamic sql, and catch the exception in the block.
--#SET TERMINATOR #
begin
declare statement varchar(128);
declare continue handle for sqlstate '42710' BEGIN END;
SET STATEMENT = 'DROP TABLE MYTABLE';
EXECUTE IMMEDIATE STATEMENT;
end #
This code will run normally in DB2. It does not need to be part of a procedure nor function.
Why not look for the table first? If you find it, it needs to be dropped; if you don't, it doesn't.
db2perf_quiet_drop that might works the way you want.. Its a free add-on :)
You can look into this post too..
http://www.dbforums.com/showthread.php?1609047-DB2-equivalent-for-mysql-s-DROP-TABLE-IF-EXISTS
If this doesn't work for you please let me know what error you are getting so I can try to help :)
Or this might work
if( NOT exists( create table detailval
(
id int,
detaildeptNo int,
info varchar(255)
);
insert into detailval(1,1, 'detail values A');
insert into detailval(2,1, 'detail values B');
insert into detailval(3,1, 'detail values C');
insert into detailval(4,2, 'detail values D');
)
)
then customStoredproc('droptable');
end if;
End
I think you should look into working with temporary tables (DECLARE GLOBAL TEMPORARY TABLE). They are stored in the temporary table space and are dropped automatically after commit.
You can easily also query syscat.tables like this:
select COUNT(*) from SYSCAT.TABLES where TRIM(TABNAME) = '<some_table_name>'
if this query returns 0 then the table does not exists.
I'm trying to get the hang of using temp tables:
CREATE OR REPLACE FUNCTION test1(user_id BIGINT) RETURNS BIGINT AS
$BODY$
BEGIN
create temp table temp_table1
ON COMMIT DELETE ROWS
as SELECT table1.column1, table1.column2
FROM table1
INNER JOIN -- ............
if exists (select * from temp_table1) then
-- work with the result
return 777;
else
return 0;
end if;
END;
$BODY$
LANGUAGE plpgsql;
I want the row temp_table1 to be deleted immediately or as soon as possible, that's why I added ON COMMIT DELETE ROWS. Obviously, I got the error:
ERROR: relation "temp_table1" already exists
I tried to add IF NOT EXISTS but I couldn't, I simply couldn't find working example of it that would be the I'm looking for.
Your suggestions?
DROP Table each time before creating TEMP table as below:
BEGIN
DROP TABLE IF EXISTS temp_table1;
create temp table temp_table1
-- Your rest Code comes here
The problem of temp tables is that dropping and recreating temp table bloats pg_attribute heavily and therefore one sunny morning you will find db performance dead, and pg_attribute 200+ gb while your db would be like 10gb.
So we're very heavy on temp tables having >500 rps and async i\o via nodejs and thus experienced a very heavy bloating of pg_attribute because of that. All you are left with is a very aggressive vacuuming which halts performance.
All answers given here do not solve this, because they all bloat pg_attribute heavily.
So the solution is elegantly this
create temp table if not exists my_temp_table (description) on commit delete rows;
So you go on playing with temp tables and save your pg_attribute.
You want to DROP term table after commit (not DELETE ROWS), so:
begin
create temp table temp_table1
on commit drop
...
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