Questions tagged [full-table-scan]
61 questions
72
votes
1 answer
Can I do a MongoDB "starts with" query on an indexed subdocument field?
I'm trying to find documents where a field starts with a value.
Table scans are disabled using notablescan.
This works:
db.articles.find({"url" : { $regex : /^http/ }})
This doesn't:
db.articles.find({"source.homeUrl" : { $regex : /^http/ }})
I…
Tom Robinson
- 8,348
- 9
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- 102
14
votes
5 answers
Issue in full table scan in cassandra
First: I know isn't a good idea do a full scan in Cassandra, however, at moment, is that what I need.
When I started look for do someting like this I read people saying wasn't possible do a full scan in Cassandra and he wasn't made to do this type…
bcfurtado
- 181
- 2
- 12
7
votes
1 answer
Why would a left join cause an optimizer to ignore an index?
Using postgres 9.6.11, I have a schema like:
owner:
id: BIGINT (PK)
dog_id: BIGINT NOT NULL (FK)
cat_id: BIGINT NULL (FK)
index DOG_ID_IDX (dog_id)
index CAT_ID_IDX (cat_id)
animal:
id: BIGINT (PK)
name: VARCHAR(50) NOT NULL
index NAME_IDX…
And1
- 113
- 6
6
votes
4 answers
Azure Table Storage - How fast can I table scan?
Everyone warns not to query against anything other than RowKey or PartitionKey in Azure Table Storage (ATS), lest you be forced to table scan. For a while, this has paralyzed me into trying to come up with exactly the right PK and RK and creating…
David Pfeffer
- 38,869
- 30
- 127
- 202
6
votes
1 answer
MySql Server System Variables --max-seeks-for-key - Practical example
I am going through documentation of MySql Indexes Optimization.
I found a setting --max-seeks-for-key=1000.I checked the "server system variables" of MySQL here.
According to it
"By setting this to a low value (say, 100), you can force MySQL to
…
cjava
- 656
- 1
- 8
- 22
5
votes
2 answers
Does postgresql keep track of full table scans it makes?
I'd like to do something similar to what's described in http://www.bestbrains.dk/Blog/2010/03/25/HowToAssertThatYourSQLDoesNotDoFullTableScans.aspx but for that I'd need postgres to keep track of any full table scans it does. Is there such a thing…
Guilherme Salgado
- 147
- 1
- 8
4
votes
1 answer
How to avoid Full Table Scan with LIKE operator
I have problem while changing a query in PL/SQL oracle with different proper query. Current query :
SELECT MAX (workzone)
FROM sccd_device_uim_tab
WHERE NAME LIKE 18075009 || '%';
my client need the query revised because :
Full…
Koyix
- 181
- 1
- 3
- 17
4
votes
4 answers
Why NonClustered index scan faster than Clustered Index scan?
As I know, heap tables are tables without clustered index and has no physical order.
I have a heap table "scan" with 120k rows and I am using this select:
SELECT id FROM scan
If I create a non-clustered index for the column "id", I get 223…
Mucida
- 603
- 9
- 24
4
votes
5 answers
Why would Oracle ignore a "perfect" index?
I have this table:
create table demo (
key number(10) not null,
type varchar2(3) not null,
state varchar2(16) not null,
... lots more columns ...
)
and this index:
create index demo_x04 on demo(key, type, state);
When I run this…
Aaron Digulla
- 321,842
- 108
- 597
- 820
3
votes
4 answers
Why isn't MySQL using my indexes when running my query?
I’m using MySQL 5.5.37. It is not an option to upgrade at this time. I have this table
CREATE TABLE `my_classroom` (
`ID` varchar(32) COLLATE utf8_bin NOT NULL DEFAULT '',
`CLASSROOM_NAME` varchar(100) COLLATE utf8_bin NOT NULL,
…
Dave
- 15,639
- 133
- 442
- 830
2
votes
1 answer
This might cause a full table scan when resolving the relationship, it is highly advised to create an index that covers this column
I have many-to-many relationship between User and Poll.
While creating the relating class below I'm getting this warning on compile time:
warning: The column pollId in the junction entity com.example.appproject.model.user.UserPollCrossRef is being…
Shimon Cohen
- 85
- 6
2
votes
1 answer
Heap vs Clustered index full table scan
I've been googling back and forth for this, and could not get a grasp of how are the table data blocks structured on the disk.
Many resources state that doing a full table scan reads the blocks sequentially (which means that the DB is able to read…
Yoni Dor
- 323
- 3
- 8
2
votes
1 answer
Dynamodb parallel scan using Table.scan api in Java
I would appreciate help from anyone familiar with how DynamoDB work.
I need to perform scan on a large DynamoDB table. I know that DynamoDBClient scan operation is limited to 1 MB size of returned data. Does the same restriction apply to Table.scan…
Tofig Hasanov
- 3,303
- 10
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- 81
2
votes
2 answers
How to understand avoid FULL TABLE SCAN
I have a table that is responsible to store log.
The DDL is this:
CREATE TABLE LOG(
"ID_LOG" NUMBER(12,0) NOT NULL ENABLE,
"DATA" DATE NOT NULL ENABLE,
"OPERATOR_CODE" VARCHAR2(20 BYTE),
"STRUCTURE_CODE" VARCHAR2(20 BYTE),
…
carlo
- 386
- 1
- 8
- 21
2
votes
1 answer
MySQL View with count() doing Full Table Scan
Consider the following view
CREATE VIEW `my_view` AS
SELECT
a.id,
(SELECT
COUNT( b.id )
FROM
another_table b
WHERE
b.a_id = a.id AND b.other_column = 'ABC'
) AS counter
FROM
…
Trevor Mills
- 409
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- 12