EXPLAIN - Hash Join

Description:

Build a hash table from the inner table, keyed by the join key. Then scan the outer table, checking if a corresponding value is present. If the hash table would exceed work_mem, this process needs to happen in several batches writing temporary files to disk, which becomes dramatically slower.

Important Fields:

• Filter
• Hash Cond
• Inner Unique
• Join Filter
• Join Type
• Rows Removed by Filter
• Rows Removed by Join Filter