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快速理解 高频对冲套利自动交易（程式化交易） - 更多技术 - 清泛网 - 专注...
...言，我才实盘测试交易15个交易日，我也不知道每月收益如何。按照估算，20万的实盘账户，每月稳定有净利润5000元以上（即，年收益大约30%以上，权益回撤不超过10%），同时，产生的手续费比净利润略低些，大约是净利润的9成...
How can I get the external SD card path for Android 4.0+?
...nment.getExternalStorageDirectory();
//Retrieve the External Storages root directory:
final String externalStorageRootDir;
if ( (externalStorageRootDir = primaryExternalStorage.getParent()) == null ) { // no parent...
Log.d(TAG, "External Storage: " + primaryExternalStorage + "...
Where should Rails 3 custom validators be stored?
...o your /config/application.rb file:
config.autoload_paths += %W["#{config.root}/lib/validators/"]
Then Rails will automatically load your validators on start up (just like /config/initializers/), but you keep the clean structure of having your validators in one nice, well named spot.
...
ruby system command check exit code
...capture it as part of your REPL command [10] pry(main)> system("touch /root/test 2> /dev/null") => false [11] pry(main)> $?.exitstatus => 0 [12] pry(main)> system("touch /root/test 2> /dev/null"); $?.exitstatus => 1
– lardcanoe
Mar 9 '1...
Is it possible to declare a variable in Gradle usable in Java?
... %c - %m%n</pattern>
</layout>
</appender>
<root level="info">
<appender-ref ref="FILE"/>
</root>
</configuration>
Files:
build.gradle
src/main/java/example/HelloWorld.java
src/test/java/example/HelloWorldTest.java
src/test/resources/logb...
How do you create a read-only user in PostgreSQL?
...user in PostgreSQL that can only do SELECTs from a particular database. In MySQL the command would be:
11 Answers
...
Do you use source control for your database items? [closed]
...
With Mysql Workbench you can have all that in a structured file(xml) that can be opened and handled with a GUI. Being xml just text, yes it can be versioning without having to type single sql sentence.
– lev...
Primary key or Unique index?
...hen it tries to insert the value 1 into this column for a second time.
In MySQL a unique constraint allows multiple NULLs.
It is possible to make a unique index on mutiple columns.
Primary key versus unique index
Things that are the same:
A primary key implies a unique index.
Things that are...
Fastest way to count exact number of rows in a very large table?
...
The fastest way by far on MySQL is:
SHOW TABLE STATUS;
You will instantly get all your tables with the row count (which is the total) along with plenty of extra information if you want.
...
Render HTML to PDF in Django site
...rServerClient(models.Manager):
def __handle_exception(self, exception_root, exception_id, exec_info ):
type, value, traceback = exec_info
raise JasperServerClientError(exception_root, exception_id), None, traceback
# 01: REPORT-METADATA
# get resource description to ...