Postgresql – Comparing Query Performance Across DBMSs

Try:

INSERT INTO T2 
SELECT NULL,T1.KEY,NULL 
FROM T1 
LEFT JOIN T2 USING (key,id)
WHERE T2.KEY IS NULL;

This should filter your join to select only those rows where there is currently no data value in T2.

(This is your original attempt, plus a new WHERE clause).

Not knowing DBeaver, I can only guess: it uses a cursor to process statement results. That has two consequences:

• Parallelization cannot be used:

  The query might be suspended during execution. In any situation in which the system thinks that partial or incremental execution might occur, no parallel plan is generated. For example, a cursor created using DECLARE CURSOR will never use a parallel plan.

• A different execution plan may be used:

  cursor_tuple_fraction (floating point)

  Sets the planner's estimate of the fraction of a cursor's rows that will be retrieved. The default is 0.1. Smaller values of this setting bias the planner towards using “fast start” plans for cursors, which will retrieve the first few rows quickly while perhaps taking a long time to fetch all rows. Larger values put more emphasis on the total estimated time. At the maximum setting of 1.0, cursors are planned exactly like regular queries, considering only the total estimated time and not how soon the first rows might be delivered.