At 01:58 PM 10/7/2011, you wrote:
Do you have any good documentation with regards creating indexes.
Also information for explain statement and what would be the desired
result of the explain statement?
This might help:
http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html
http://www.site
The second index you specified '(field_b, field_a)' would be usable when
querying on field_b alone, or both fields in conjunction. This particular
index is of no value should you be querying 'field_a' alone. Then that
first index '(field_a, field_b)' would apply.
- md
On Fri, Oct 7, 2011 at 2:
Do you have any good documentation with regards creating indexes. Also
information for explain statement and what would be the desired result of the
explain statement?
On 7 Oct 2011, at 17:10, Michael Dykman wrote:
> How heavily a given table is queried does not directly affect the index size,
Can you give more information as to why the second index would be of no use ?
On 7 Oct 2011, at 18:24, Michael Dykman wrote:
> No, I don't think it can be called. It is a direct consequence of the
> relational paradigm. Any implementation of an RDBMS has the same
> characteristic.
>
> - md
No, I don't think it can be called. It is a direct consequence of the
relational paradigm. Any implementation of an RDBMS has the same
characteristic.
- md
On Fri, Oct 7, 2011 at 12:20 PM, Reindl Harald wrote:
> but could this not be called a bug?
>
> Am 07.10.2011 18:08, schrieb Michael Dykm
but could this not be called a bug?
Am 07.10.2011 18:08, schrieb Michael Dykman:
> When a query selects on field_a and field_b, that index can be used. If
> querying on field_a alone, the index again is useful. Query on field_b
> alone however, that first index is of no use to you.
>
> On Fri,
How heavily a given table is queried does not directly affect the index
size, only the number and depth of the indexes.
No, it is not that unusual to have the index file bigger. Just make sure
that every index you have is justified by the queries you are making against
the table.
- md
On Fri,
When a query selects on field_a and field_b, that index can be used. If
querying on field_a alone, the index again is useful. Query on field_b
alone however, that first index is of no use to you.
On Fri, Oct 7, 2011 at 10:49 AM, Brandon Phelps wrote:
> This thread has sparked my interest. What
This thread has sparked my interest. What is the difference between an index on
(field_a, field_b) and an index on (field_b, field_a)?
On 10/06/2011 07:43 PM, Nuno Tavares wrote:
Neil, whenever you see multiple fields you'd like to index, you should
consider, at least:
* The frequency of each
Is it normal practice for a heavily queried MYSQL tables to have a index
file bigger than the data file ?
On Fri, Oct 7, 2011 at 12:22 AM, Michael Dykman wrote:
> Only one index at a time can be used per query, so neither strategy is
> optimal. You need at look at the queries you intend to run
Neil, whenever you see multiple fields you'd like to index, you should
consider, at least:
* The frequency of each query;
* The occurrences of the same field in multiple queries;
* The cardinality of each field;
There is a tool "Index Analyzer" that may give you some hints, and I
think it's maatk
Only one index at a time can be used per query, so neither strategy is
optimal. You need at look at the queries you intend to run against the
system and construct indexes which support them.
- md
On Thu, Oct 6, 2011 at 2:35 PM, Neil Tompkins
wrote:
> Maybe that was a bad example. If the query
Maybe that was a bad example. If the query was name = 'Red' what index should
I create ?
Should I create a index of all columns used in each query or have a index on
individual column ?
On 6 Oct 2011, at 17:28, Michael Dykman wrote:
> For the first query, the obvious index on score will give
For the first query, the obvious index on score will give you optimal
results.
The second query is founded on this phrase: "Like '%Red%' " and no index
will help you there. This is an anti-pattern, I am afraid. The only way
your database can satisfy that expression is to test each and every reco
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