[Solved] missing FROM-clause entry for table on postgresql

How to optimize this SQL query?

In case you have your own slow SQL query, you can optimize it automatically here.

For the query above, the following recommendations will be helpful as part of the SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
  2. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
Optimal indexes for this query:
CREATE INDEX databaseone_idx_id ON "databaseone" ("id");
CREATE INDEX databasetwo_idx_item_id ON "databasetwo" ("item_id");
The optimized query:
SELECT
        databaseone.*,
        COUNT(databasetwo) AS total_items 
    FROM
        databaseone 
    LEFT JOIN
        databasetwo 
            ON (
                databaseone.id = databasetwo.item_id
            ) 
    GROUP BY
        databaseone.id 
    ORDER BY
        databaseone.id ASC

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* original question posted on StackOverflow here.