![]() Is this the right way to do it? This is the first time I am doing something with a temp table. SELECT INTO works in SQL but not PL/pgSQL. ![]() INSERT into product_temp_mapping (accountid, productUID, sampleproductId) I want to use SELECT INTO to make a temporary table in one of my functions. PostgreSQL automatically drops the temporary tables at the end of a session or a transaction. Hint: If you want to discard the results of a SELECT, use PERFORM instead.ĬREATE TEMP TABLE IF NOT EXISTS product_temp_mappingįOREACH sampleproductId IN ARRAY productIds When I try to get the data back from the table I get an error: ERROR: query has no destination for result data I’m also available for consulting if you just don’t have time for that and need to solve performance problems quickly.I am creating a temp table, and am fetching data from multiple tables and inserting data into it. I’m offering a 75% discount to my blog readers if you click from here. If this is the kind of SQL Server stuff you love learning about, you’ll love my training. Next time you’re tuning a query and want to drop some data into a temp table, you should experiment with this technique. The data is not returned to the client, as it is with a normal SELECT. If we crank one of the queries that gets a serial insert up to DOP 12, we lose some speed when we hit the table. SELECT INTO creates a new table and fills it with data computed by a query. Though the speed ups above at higher DOPs are largely efficiency boosters while reading from the Posts table, the speed does stay consistent through the insert. The PostgreSQL usage of SELECT INTO to represent table creation is historical. This indeed is the usage found in ECPG (see Chapter 33) and PL/pgSQL (see Chapter 39 ). If you start experimenting with this trick, and don’t see noticeable improvements at your current DOP, you may need to bump it up to see throughput increases.Īlso remember that if you’re doing this with clustered column store indexes, it can definitely make things worse. The SQL standard uses SELECT INTO to represent selecting values into scalar variables of a host program, rather than creating a new table. CREATE TEMP TABLE temptable AS WITH t (k, v) AS ( VALUES (0::int,-99999::numeric), (1::int,100::numeric) ) SELECT FROM t Note, also from the comments by ahorsewithnoname, and in the OP's original question, this includes a cast to the correct datatypes inside the values list and uses a CTE (WITH) statement. The query syntax to create a temporary table is as the following. At DOP 4, the insert really isn’t any faster than the serial insert. In SQL Server you can use a SELECT INTO statement to create a temporary table based on the query results. Syntax to create PostgreSQL Temporary tables. Note the execution times dropping as DOP increases. CREATE TEMPORARY TABLE users ( id int, name VARCHAR(80)) Now, we will add some data into the temporary ‘users’ table. We will create the temporary ‘users’ table by using the following CREATE table statement. Here are the query plans for 3 fully parallel inserts into an empty, index-less temp #table. Output: We will create a temporary table with the same name, ‘users,’ as the permanent table we have created. Another little thing we may need to tinker with is DOP. It’s the little things we do that often end up making the biggest differences. ![]() INSERT #tp WITH(TABLOCK) which is sort of annoying.īut you know. When it comes to parallel inserts, you do need the TABLOCK, or TABLOCKX hint to get it, e.g. In PostgreSQL, the SELECT INTO statement creates a new table, copies data from the original table, and pastes it into the newly created table. To do that, we are using the SELECT INTO TEMP TABLE. I want to copy the list of movies with an NC-17 rating to the temporary table named tblNC17Movies. If your goal is the fastest possible insert, you may want to create the index later. In this example, we will see how to insert data in the PostgreSQL temporary table within the script. The first thing to note is that inserting into an indexed temp table, parallel or not, does slow things down. The demo code is available here if you’d like to test it out. If your temp table has indexes, primary keys, or an identity column, you won’t get the parallel insert no matter how hard you try. pattern, you’re probably not, and, well, that could be holding you back. INTO #some_table pattern, you’re probably already getting parallel inserts. If your code is already using the SELECT. Remember that you can’t insert into variables in parallel, unless you’re extra sneaky. In PostgreSQL you can also use SELECT INTO. ![]() If you have a workload that uses #temp tables to stage intermediate results, and you probably do because you’re smart, it might be worth taking advantage of being able to insert into the #temp table in parallel. In SQL Server you can use a SELECT INTO statement to create a temporary table based on the query results.
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