英語 での The optimizer の使用例とその 日本語 への翻訳
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The optimizer has no other choice than to"guess.
Responsibility for building the optimizer was handed off to Wagner.
Can I hint the optimizer by giving the range of an integer?
In both these cases, the WHERE clause is transformed by the optimizer into WHERE region_code IN(3, 4, 5).
When the optimizer takes index extensions into account, it treats k_d as(d, i1, i2).
If the database still uses an explicit sort operation, the optimizer prefers this plan due to its cost value;
When the optimizer does not consider index extensions, it treats the index k_d as only(d).
If an index can nolonger be used for an index-only scan, the optimizer will choose the next best execution plan.
In the end, the optimizer will choose the outer and inner tables based on detailed cost estimates.
Just look at the row count estimate in the execution plan: the optimizer expects to aggregate more than 40,000 rows.
The optimizer tries to see if this index is usable(possible_keys field), this is all very logical.
If n is omitted or if it is outside the allowed range, the optimizer assigns the number of times to unroll the loop.
The optimizer uses it to determine the frequency of the subsidiary ID mentioned in the SQL query.
Should the data change,the explicit estimate may become inaccurate and may force the optimizer to select poor plans.
Fast Disk Optimization: The optimizer rearranges all data and places them to the beginning of the drive.
NoteStatements without bind parameters can be explained directly:EXPLAIN SELECT 1In this case, the optimizer has always considered the actual values during query planning.
That means the optimizer might select an entirely different execution plan or, as above, a similar execution plan with another index.
If we do not use bind parameters butwrite the actual values in the SQL statement, the optimizer selects the proper index for the active filter:.
For example, the optimizer assumes that the result of"undef& 1" has zeros for its top bits, treating only the low bit as undefined.
If you know that there is always a leading wildcard,you can obfuscate the LIKE condition intentionally so that the optimizer can no longer consider the index on LAST_NAME.
In doing so, the Optimizer takes into account special kinematic properties of the machine and user-specific properties for collision avoidance.
When the optimizer script executes, this cookie stores the variation this visitor is assigned to for each experiment, so the visitor has a consistent experience on your site.
In addition to information on hardware and software, the optimizer includes several tools for system tuning and countless tweaks for faster booting and shutting down the computer.
Instead, the optimizer can use the secondary index k_d on(d), and the execution plan depends on whether the extended index is used.
For example, the optimizer assumes that the result of"undef& 1" has zeros for its top bits, treating only the low bit as undefined.
In MySQL 8.0, the optimizer can perform a partial, in-place update of a JSON column instead of removing the old document and writing the new document in its entirety to the column.