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【BLE技术内幕】BLE技术揭秘 - 创客硬件开发 - 清泛IT论坛，有思想、有深度
文章源自：http://doc.iotxx.com/index.php?title=BLE技术揭秘
BLE技术揭秘
BLE是低功耗蓝牙的英文缩写（Bluetooth Low Energy），是蓝牙4.0版本起开始支持的新的、低功耗版本的蓝牙技术规范。蓝牙技术联盟（Bluetooth SIG）在2010年发布了跨...
Does PostgreSQL support “accent insensitive” collations?
...eded).
SELECT *
FROM users
WHERE unaccent(name) = unaccent('João');
Index
To use an index for that kind of query, create an index on the expression. However, Postgres only accepts IMMUTABLE functions for indexes. If a function can return a different result for the same input, the index could...
How do I create an HTML table with a fixed/frozen left column and a scrollable body?
...
scrolled-td-table td-cells.
*/
position: relative;
z-index: 1;
}
.scrolled-td-table-wrapper td {
/* Place scrolled-td-table td-cells
above fixed-th-table.
*/
position: relative;
}
.scrolled-td-table-wrapper {
/* Make horizonal scrollbar if needed */
ov...
No route matches [GET] /assets
... expires max;
add_header Cache-Control public;
}
try_files $uri/index.html $uri @puma;
location @puma {
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_redirect off;
proxy_pass http://puma;
}
error_page 500 502 5...
Getting a list item by index
...g c# moving over from Java. I can't seem to find how to get a list item by index. In java to get the first item of the list it would be:
...
SQL - many-to-many table primary key
...r col1 and col2 values in the referenced tables are unique) and a separate index on (col2,col1) will catch those cases where the opposite order would execute faster. The surrogate is a waste of space.
You won't need indexes on the individual columns since the table should only ever be used to join ...
Create an array with same element repeated multiple times
...f the entries up front, with arr = new Array(len);, then assign to them by index in the loop, i.e. arr[i] = value;. That way you only pay O(n) rather than having to keep reallocating the array as it grows. In general, it's always better to avoid growing arrays by appending when possible. If you k...
Ways to iterate over a list in Java
..., only if you do it through the remove method of the iterator itself. With index-based iteration, you are free to modify the list in any way. However, adding or removing elements that come before the current index risks having your loop skipping elements or processing the same element multiple times...
Numpy argsort - what is it doing?
...ocumentation
Returns the indices that would sort an array.
2 is the index of 0.0.
3 is the index of 0.1.
1 is the index of 1.41.
0 is the index of 1.48.
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What's the “average” requests per second for a production web application?
... second vs. requests per second. I think requests/second is in that same ballpark(100 to 200) but with streaming it shoots up to 1140 records / second (doing ndjson). Anyways thought I would share more numbers. (not sure if this will change as that was tested streamed through 2 microservices into...