Overview
Artifact ID: | d1fbaa0a04dabea0a6bd4f063f9a228a3c279660 |
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Ticket: | d805526eae253103dc307740dcf859b6d701c2f4
Incorrect join result or assertion fault due to transitive constraints |
User & Date: | drh 2013-07-08 18:02:53 |
Changes
- foundin changed to: "3.7.17"
- icomment:
The following SQL should return a single row of result. But due to the transitive constraint optimization, it either hits an assertion fault or it returns zero rows (depending on whether the SQLITE_DEBUG compile-time option is used.) Note that SQLITE_ENABLE_STAT3 is required for this bug to appear. <blockquote><verbatim> CREATE TABLE t1(w INTEGER PRIMARY KEY, x); CREATE TABLE t2(y INTEGER, z); INSERT INTO t1 VALUES(1,2); INSERT INTO t2 VALUES(1,3); SELECT * FROM t1 CROSS JOIN t2 WHERE w=y AND y IS NOT NULL; </verbatim></blockquote> The problem appears to have been introduced by check-in [38852f158ab]. Low-level technical details: The "y IS NOT NULL" constraint is translated into a "y>NULL" virtual constraint when SQLITE_ENABLE_STAT3 is defined. The y>NULL constraint tagged to indicate that the usual not-NULL check on the right-hand side should be skipped since this is an artificial constraint. The normal index handler knows to check for that tag and skip the not-NULL check. But after the transitive constraints were added, there is now also a "w>NULL" virtual constraint (because w=x). The w>NULL constraint is also tagged, but the INTEGER PRIMARY KEY handlers does not know to check for that tag and to skip the not-NULL check. It sees that the right-hand side of the constraint is NULL and all fails the constraint, resulting in no output rows.
- login: "drh"
- mimetype: "text/x-fossil-wiki"
- severity changed to: "Severe"
- status changed to: "Open"
- title changed to:
Incorrect join result or assertion fault due to transitive constraints
- type changed to: "Code_Defect"