Query Performance When Dropping Multiple Columns

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In PostgreSQL, is there any performance gain when using a single ALTER TABLE statement to drop multiple columns, instead of using a separate statement to drop each column?



ALTER TABLE table DROP COLUMN col1, DROP COLUMN col2, DROP COLUMN 3;

// vs

ALTER TABLE table DROP COLUMN col1;
ALTER TABLE table DROP COLUMN col2;
ALTER TABLE table DROP COLUMN col3;



postgresql query-performance alter-table




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  • I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
    – Tamer Shlash
    Aug 28 at 7:26
















up vote
1
down vote

favorite












In PostgreSQL, is there any performance gain when using a single ALTER TABLE statement to drop multiple columns, instead of using a separate statement to drop each column?



ALTER TABLE table DROP COLUMN col1, DROP COLUMN col2, DROP COLUMN 3;

// vs

ALTER TABLE table DROP COLUMN col1;
ALTER TABLE table DROP COLUMN col2;
ALTER TABLE table DROP COLUMN col3;



postgresql query-performance alter-table




share|improve this question




















  • I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
    – Tamer Shlash
    Aug 28 at 7:26












up vote
1
down vote

favorite









up vote
1
down vote

favorite











In PostgreSQL, is there any performance gain when using a single ALTER TABLE statement to drop multiple columns, instead of using a separate statement to drop each column?



ALTER TABLE table DROP COLUMN col1, DROP COLUMN col2, DROP COLUMN 3;

// vs

ALTER TABLE table DROP COLUMN col1;
ALTER TABLE table DROP COLUMN col2;
ALTER TABLE table DROP COLUMN col3;



postgresql query-performance alter-table




share|improve this question












In PostgreSQL, is there any performance gain when using a single ALTER TABLE statement to drop multiple columns, instead of using a separate statement to drop each column?



ALTER TABLE table DROP COLUMN col1, DROP COLUMN col2, DROP COLUMN 3;

// vs

ALTER TABLE table DROP COLUMN col1;
ALTER TABLE table DROP COLUMN col2;
ALTER TABLE table DROP COLUMN col3;




postgresql query-performance alter-table





share|improve this question











share|improve this question




share|improve this question










asked Aug 28 at 7:25









Tamer Shlash

1084




1084











  • I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
    – Tamer Shlash
    Aug 28 at 7:26
















  • I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
    – Tamer Shlash
    Aug 28 at 7:26















I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
– Tamer Shlash
Aug 28 at 7:26




I put this question here because it is about query-performance, a topic covered by this site. If it belongs to SO please let me know.
– Tamer Shlash
Aug 28 at 7:26










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Yes, but it's too small to be noticed unless you plan to drop hundreds or even thousands of columns ;)



Each drop column is executed separately regardless if it's a separate statement, or part of a statement. The performance gain would be in the work postgres do before and after each statement, for instance taking a lock on the table, creating implicit transactions, and parsing the statement which it would only have to do once if all columns are dropped in one statement.






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    1 Answer
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    1 Answer
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    active

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    up vote
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    down vote



    accepted










    Yes, but it's too small to be noticed unless you plan to drop hundreds or even thousands of columns ;)



    Each drop column is executed separately regardless if it's a separate statement, or part of a statement. The performance gain would be in the work postgres do before and after each statement, for instance taking a lock on the table, creating implicit transactions, and parsing the statement which it would only have to do once if all columns are dropped in one statement.






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      up vote
      3
      down vote



      accepted










      Yes, but it's too small to be noticed unless you plan to drop hundreds or even thousands of columns ;)



      Each drop column is executed separately regardless if it's a separate statement, or part of a statement. The performance gain would be in the work postgres do before and after each statement, for instance taking a lock on the table, creating implicit transactions, and parsing the statement which it would only have to do once if all columns are dropped in one statement.






      share|improve this answer






















        up vote
        3
        down vote



        accepted







        up vote
        3
        down vote



        accepted






        Yes, but it's too small to be noticed unless you plan to drop hundreds or even thousands of columns ;)



        Each drop column is executed separately regardless if it's a separate statement, or part of a statement. The performance gain would be in the work postgres do before and after each statement, for instance taking a lock on the table, creating implicit transactions, and parsing the statement which it would only have to do once if all columns are dropped in one statement.






        share|improve this answer












        Yes, but it's too small to be noticed unless you plan to drop hundreds or even thousands of columns ;)



        Each drop column is executed separately regardless if it's a separate statement, or part of a statement. The performance gain would be in the work postgres do before and after each statement, for instance taking a lock on the table, creating implicit transactions, and parsing the statement which it would only have to do once if all columns are dropped in one statement.







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        answered Aug 28 at 8:16









        Jimmy Stenke

        61335




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