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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3926) Incorrect ORDER BY caused by index
Date Fri, 20 Mar 2009 19:00:52 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12683990#action_12683990
] 

Mamta A. Satoor commented on DERBY-3926:
----------------------------------------

The query plan when the incorrect results are returned is as follows
Statement Name:
        null
Statement Text:
        SELECT table1.id, m0.value, m1.value FROM table1, table2 m0, table2 m1 W
HERE table1.id=m0.id AND
m0.name='PageSequenceId' AND table1.id=m1.id AND m1.name='PostComponentId' AND m
1.value='21857' ORDER BY
m0.value
Parse Time: 0
Bind Time: 0
Optimize Time: 0
Generate Time: 0
Compile Time: 0
Execute Time: 0
Begin Compilation Timestamp : null
End Compilation Timestamp : null
Begin Execution Timestamp : null
End Execution Timestamp : null
Statement Execution Plan Text:
Project-Restrict ResultSet (10):
Number of opens = 1
Rows seen = 3
Rows filtered = 0
restriction = false
projection = true
        constructor time (milliseconds) = 0
        open time (milliseconds) = 0
        next time (milliseconds) = 0
        close time (milliseconds) = 0
        restriction time (milliseconds) = 0
        projection time (milliseconds) = 0
        optimizer estimated row count:            0.00
        optimizer estimated cost:            3.52

Source result set:
        Nested Loop Join ResultSet:
        Number of opens = 1
        Rows seen from the left = 168
        Rows seen from the right = 3
        Rows filtered = 0
        Rows returned = 3
                constructor time (milliseconds) = 0
                open time (milliseconds) = 0
                next time (milliseconds) = 0
                close time (milliseconds) = 0
                optimizer estimated row count:            0.00
                optimizer estimated cost:            3.52

        Left result set:
                Nested Loop Join ResultSet:
                Number of opens = 1
                Rows seen from the left = 3
                Rows seen from the right = 168
                Rows filtered = 0
                Rows returned = 168
                        constructor time (milliseconds) = 0
                        open time (milliseconds) = 0
                        next time (milliseconds) = 0
                        close time (milliseconds) = 0
                        optimizer estimated row count:            0.00
                        optimizer estimated cost:            3.52

                Left result set:
                        Project-Restrict ResultSet (5):
                        Number of opens = 1
                        Rows seen = 3
                        Rows filtered = 0
                        restriction = true
                        projection = true
                                constructor time (milliseconds) = 0
                                open time (milliseconds) = 0
                                next time (milliseconds) = 0
                                close time (milliseconds) = 0
                                restriction time (milliseconds) = 0
                                projection time (milliseconds) = 0
                                optimizer estimated row count:            0.00
                                optimizer estimated cost:            3.52

                        Source result set:
                                Index Row to Base Row ResultSet for TABLE2:
                                Number of opens = 1
                                Rows seen = 3
                                Columns accessed from heap = {0, 1, 2}
                                        constructor time (milliseconds) = 0
                                        open time (milliseconds) = 0
                                        next time (milliseconds) = 0
                                        close time (milliseconds) = 0
                                        optimizer estimated row count:  0.00
                                        optimizer estimated cost:            3.52
                                        Index Scan ResultSet for TABLE2 using index KEY3 at
read committed isolation level using share row locking chosen by the optimizer
                                        Number of opens = 1
                                        Rows seen = 3
                                        Rows filtered = 0
                                        Fetch Size = 1
                                                constructor time (milliseconds)= 0
                                                open time (milliseconds) = 0
                                                next time (milliseconds) = 0
                                                close time (milliseconds) = 0
                                                next time in milliseconds/row =0
                                        scan information:
                                                Bit set of columns fetched=All
                                                Number of columns fetched=2
                                                Number of deleted rows visited=0

                                                Number of pages visited=2
                                                Number of rows qualified=3
                                                Number of rows visited=4
                                                Scan type=btree
                                                Tree height=-1
                                                start position:
        >= on first 1 column(s).
        Ordered null semantics on the following columns:

                                                stop position:
        > on first 1 column(s).
        Ordered null semantics on the following columns:

                                                qualifiers:None
                                                optimizer estimated row count:        0.00
                                                optimizer estimated cost:     3.52


                Right result set:
                        Project-Restrict ResultSet (8):
                        Number of opens = 3
                        Rows seen = 8688
                        Rows filtered = 8520
                        restriction = true
                        projection = true
                                constructor time (milliseconds) = 0
                                open time (milliseconds) = 0
                                next time (milliseconds) = 0
                                close time (milliseconds) = 0
                                restriction time (milliseconds) = 0
                                projection time (milliseconds) = 0
                                optimizer estimated row count:            0.00
                                optimizer estimated cost:            0.00

                        Source result set:
                                Index Row to Base Row ResultSet for TABLE2:
                                Number of opens = 3
                                Rows seen = 8688
                                Columns accessed from heap = {0, 1, 2}
                                        constructor time (milliseconds) = 0
                                        open time (milliseconds) = 0
                                        next time (milliseconds) = 0
                                        close time (milliseconds) = 0
                                        optimizer estimated row count:  0.00
                                        optimizer estimated cost:            0.00

                                        Index Scan ResultSet for TABLE2 using index KEY3 at
read committed isolation level using share row locking chosen by the
 optimizer
                                        Number of opens = 3
                                        Rows seen = 8688
                                        Rows filtered = 0
                                        Fetch Size = 1
                                                constructor time (milliseconds)= 0
                                                open time (milliseconds) = 0
                                                next time (milliseconds) = 0
                                                close time (milliseconds) = 0
                                                next time in milliseconds/row =0

                                        scan information:
                                                Bit set of columns fetched={1}
                                                Number of columns fetched=1
                                                Number of deleted rows visited=0

                                                Number of pages visited=12
                                                Number of rows qualified=8688
                                                Number of rows visited=8688
                                                Scan type=btree
                                                Tree height=2
                                                start position:        None
                                                stop position:        None
                                                qualifiers:None
                                                optimizer estimated row count:          0.00
                                                optimizer estimated cost:     0.00



        Right result set:
                Table Scan ResultSet for TABLE1 at read committed isolation level using instantaneous
share row locking chosen by the optimizer
                Number of opens = 168
                Rows seen = 3
                Rows filtered = 0
                Fetch Size = 16
                        constructor time (milliseconds) = 0
                        open time (milliseconds) = 0
                        next time (milliseconds) = 0
                        close time (milliseconds) = 0
                        next time in milliseconds/row = 0

                scan information:
                        Bit set of columns fetched=All
                        Number of columns fetched=1
                        Number of pages visited=1
                        Number of rows qualified=3
                        Number of rows visited=9408
                        Scan type=heap
                        start position:
null                    stop position:
null                    qualifiers:
Column[0][0] Id: 0
Operator: =
Ordered nulls: false
Unknown return value: false
Negate comparison result: false
Column[0][1] Id: 0
Operator: =
Ordered nulls: false
Unknown return value: false
Negate comparison result: false

                        optimizer estimated row count:            0.00
                        optimizer estimated cost:            0.00

> Incorrect ORDER BY caused by index
> ----------------------------------
>
>                 Key: DERBY-3926
>                 URL: https://issues.apache.org/jira/browse/DERBY-3926
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.4.2.0
>            Reporter: Tars Joris
>         Attachments: derby-reproduce.zip
>
>
> I think I found a bug in Derby that is triggered by an index on a large column: VARCHAR(1024).
I know it  is generally not a good idea to have an index on such a large column.
> I have a table (table2) with a column "value", my query orders on this column but the
result is not sorted. It is sorted if I remove the index on that column.
> The output of the attached script is as follows (results should be ordered on the middle
column):
> ID                  |VALUE        |VALUE
> ----------------------------------------------
> 2147483653          |000002       |21857
> 2147483654          |000003       |21857
> 4294967297          |000001       |21857
> While I would expect:
> ID                  |VALUE        |VALUE
> ----------------------------------------------
> 4294967297          |000001       |21857
> 2147483653          |000002       |21857
> 2147483654          |000003       |21857
> This is the definition:
> CREATE TABLE table1 (id BIGINT NOT NULL, PRIMARY KEY(id));
> CREATE INDEX key1 ON table1(id);
> CREATE TABLE table2 (id BIGINT NOT NULL, name VARCHAR(40) NOT NULL, value VARCHAR(1024),
PRIMARY KEY(id, name));
> CREATE UNIQUE INDEX key2 ON table2(id, name);
> CREATE INDEX key3 ON table2(value);
> This is the query:
> SELECT table1.id, m0.value, m1.value
> FROM table1, table2 m0, table2 m1
> WHERE table1.id=m0.id
> AND m0.name='PageSequenceId'
> AND table1.id=m1.id
> AND m1.name='PostComponentId'
> AND m1.value='21857'
> ORDER BY m0.value;
> The bug can be reproduced by just executing the attached script with the ij-tool.
> Note that the result of the query becomes correct when enough data is changed. This prevented
me from creating a smaller example.
> See the attached file "derby-reproduce.zip" for sysinfo, derby.log and script.sql.
> Michael Segel pointed out:
> "It looks like its hitting the index ordering on id,name from table 2 and is ignoring
the order by clause."

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