DELETE Weirdness - Mailing list pgsql-general

From Ravi Chemudugunta
Subject DELETE Weirdness
Date
Msg-id 7a4208ef1001141655l1a6ffa82u9d884d24b23967bd@mail.gmail.com
Whole thread Raw
Responses Re: DELETE Weirdness  (Jeff Davis <pgsql@j-davis.com>)
List pgsql-general
There are two ways of deleting things,

DELETE FROM <table> WHERE PK IN ( ...SET... );

DELETE FROM <table> USING <table2>
WHERE <join condition> AND <filter clause>;

I am deleting from a table where the rows are inter-related (it is a
tree); using the first version with IN, it does not delete all rows;
there is a trigger that rearranges the rows when a row is deleted
(updating references etc.).  Disabling this trigger results in correct
behavoir.

However, using the second version (using USING) works as expected with
or without disabling the said triggers.

I cannot quite understand this; Are the contents of the IN query
worked out ONCE per outer query and therefore become invalid when
DELETE comes along and changes items that were part of the set ? (for
e.g.)



-ravi

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:wq

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