I am having a few issues with trying to live in a subsonic world and being a subsonic girl when it comes to subsonic expressions....
after reading Subsonic Query (ConditionA OR ConditionB) AND ConditionC it would appear i am not the only one with this sort of issue but hopefully someone (the almighty rob??) can answer this.
i am attempting to create an expression in my query based on a looping condition. what i want to achieve (in pseudo code) is something like this:
objQuery.andexpressionstart();
foreach (condition in conditions){
if (condition){
objQuery.and(conditionColumn).isequalto(X);
}
}
objQuery.expressionstop();
my main issue is that each condition that is inside the expression is a different column - otherwise i could just use .In() . i also have extra search criteria (read a fair bit) outside so it can't be outside an expression.
i REALLY don't want to leave the warm coseyness of the strongly-typed-subsonic womb however i think in this instance i might have too... if i DO have to is there a way to add to a subsonic query with a hand typed condition so i don't have to change all the other code in the query (alot of business logic living in subsonic land right now)
As always, thanks for any help
cheers
I haven't the time to test this right now, but I think if you do something like the following should work:
bool isFirstCondition = true;
foreach (condition in conditions){
if (condition)
{
if(isFirstCondition)
{
objQuery.AndExpression(conditionColumn).isequalto(X);
isFirstCondition = false;
}
else
{
objQuery.and(conditionColumn).isequalto(X);
}
}
}
Make sure all your other conditions have been added prior to the loop.
Related
I have something like this, using Akka, Alpakka + Slick
Slick
.source(
sql"""select #${onlyTheseColumns.mkString(",")} from #${dbSource.table}"""
.as[Map[String, String]]
.withStatementParameters(rsType = ResultSetType.ForwardOnly, rsConcurrency = ResultSetConcurrency.ReadOnly, fetchSize = batchSize)
.transactionally
).map( doSomething )...
I want to update this plain sql query with skipping the first N-th element.
But that is very DB specific.
Is is possible to get the pagination bit generated by Slick? [like for type-safe queries one just do a drop, filter, take?]
ps: I don't have the Schema, so I cannot go the type-safe way, just want all tables as Map, filter, drop etc on them.
ps2: at akka level, the flow.drop works, but it's not optimal/slow, coz it still consumes the rows.
Cheers
Since you are using the plain SQL, you have to provide a workable SQL in code snippet. Plain SQL may not type-safe, but agile.
BTW, the most optimal way is to skip N-th element by Database, such as limit in mysql.
depending on your database engine, you could use something like
val page = 1
val pageSize = 10
val query = sql"""
select #${onlyTheseColumns.mkString(",")}
from #${dbSource.table}
limit #${pageSize + 1}
offset #${pageSize * (page - 1)}
"""
the pageSize+1 part tells you whether the next page exists
I want to update this plain sql query with skipping the first N-th element. But that is very DB specific.
As you're concerned about changing the SQL for different databases, I suggest you abstract away that part of the SQL and decide what to do based on the Slick profile being used.
If you are working with multiple database product, you've probably already abstracted away from any specific profile, perhaps using JdbcProfile. In that case you could place your "skip N elements" helper in a class and use the active slickProfile to decide on the SQL to use. (As an alternative you could of course check via some other means, such as an environment value you set).
In practice that could be something like this:
case class Paginate(profile: slick.jdbc.JdbcProfile) {
// Return the correct LIMIT/OFFSET SQL for the current Slick profile
def page(size: Int, firstRow: Int): String =
if (profile.isInstanceOf[slick.jdbc.H2Profile]) {
s"LIMIT $size OFFSET $firstRow"
} else if (profile.isInstanceOf[slick.jdbc.MySQLProfile]) {
s"LIMIT $firstRow, $size"
} else {
// And so on... or a default
// Danger: I've no idea if the above SQL is correct - it's just placeholder
???
}
}
Which you could use as:
// Import your profile
import slick.jdbc.H2Profile.api._
val paginate = Paginate(slickProfile)
val action: DBIO[Seq[Int]] =
sql""" SELECT cols FROM table #${paginate.page(100, 10)}""".as[Int]
In this way, you get to isolate (and control) RDBMS-specific SQL in one place.
To make the helper more usable, and as slickProfile is implicit, you could instead write:
def page(size: Int, firstRow: Int)(implicit profile: slick.jdbc.JdbcProfile) =
// Logic for deciding on SQL goes here
I feel obliged to comment that using a splice (#$) in plain SQL opens you to SQL injection attacks if any of the values are provided by a user.
How do you do something like gun.get({startkey, endkey}) ?
Previously: https://github.com/amark/gun/issues/479
#qwe123wsx #sebastianmacias apologies for the delay! Originally posted at: https://github.com/amark/gun/issues/479
The wire spec has a protocol for this but it isn't implemented yet. It looks something like this:
gun.on('out', {get: {'#': {'>': 'a', '<': 'b'}}});
However this doesn't work yet. I would recommend instead:
(1) Pagination behavior is very different from one app to another and will be hard for us to create a "one-size-fits-all" solution, so it would be highly helpful if you could implement your own* pagination and make it available as a user-module, then we can learn from your experience (what worked, what didn't) and make the best solution part of core.
(2) Your app will probably work fine without pagination in the meanwhile, while it can be built (it is targeted for after 1.0), and then as your app becomes more popular, it should be fairly easy to add in without much refactor, once you need it and it is available.
... * How to build your own?
Lots of good articles on this, best one I've seen yet is from Neo4j on how to do it in a graph database (which applies to gun as well) https://graphaware.com/neo4j/2014/08/20/graphaware-neo4j-timetree.html .
Another rough idea is you model your data based on pagination or time. So rather than having ALL tweets go into user's tweet table, instead, the user's tweet table is a table of DAYS (or weeks), and then you put the tweet inside the week table. Now when you load the data, you can scan/skip based off of week very easily while it being super bandwidth efficient.
Rough PSEUDO code:
function onTweetSend(tweet){
gun.get('user').get('alice').get('tweets').get(Date.uniqueYear() + Date.uniqueWeek()).set(tweet)
}
function paginateUserTweet(howMany, cb){
var range = convertToArrayOfUniqueWeekNamesFromToday(howMany);
var all = [];
range.forEach(function(week){
gun.get('user').get('alice').get('tweets').get(week).load(function(tweets){
all.push(tweets);
if(all.length < range.length){ return }
all = flattenArray(all);
cb(all);
});
});
}
Now we can use https://gun.eco/docs/RAD#lex
gun.get(...).get({'.': {'>': startkey, '<': endkey}, '%': 50000}).map().once(...)
In my controller method for the the index view I have the following line.
#students_instance = Student.includes(:memo_tests => {:memo_target => :memo_level})
So for each Student I eager-load all necessary info.
Later on in a .map block, I call the .where() method on one of the relations as shown below.
#all_students = #students_instance.map do |student|
...
last_pass = student.memo_tests.where(:result => true).last.created_at.utc
difference_in_weeks = ((last_pass.to_i - current_date.to_i) / 1.week).round
...
end
This leads to a single SQL query for each student. And since I have over 300+ students, leads to very slow load times and over 300+ SQL queries.
Am I right in thinking that this is caused by the .where() method. I think this because I have checked everything else and these are the two lines that cause all of the queries.
More importantly, is there a better way to do this that reduces these queries to a single query?
The moment you ask where, the statement is translated to a query. Normally, the result should be sql-cached...
Anyway, in order to be sure, you can instead add programming logic to your statement. That way, you are not requesting a NEW sql statement.
last_pass = student.memo_tests.map {|m| m.created_at if m.result}.compact.sort.last
EDIT
I see the OP's question does not require sorting... So, leaving the sorting out:
last_pass = student.memo_tests.map {|m| m.created_at if m.result}.compact.last
compact is required to remove nil results from the array.
developers, I need again your help.
I work with a very big MS SQL database, records in this db more than 1kk.
So, when i try to make query, i get error with limiting binding of 2100 parameters. I try to make also query with DB::raw, but it doesn't help.
I not want to make a pure SQL query. Any solutions?
$product_codes = array_slice($product_codes, 0, 1999); // in original $product_codes about 4k codes.
$wheels = Wheel::select(array('Wheel_Size'))->whereIn('Product_code', $product_codes)->lists('Wheel_Size');
Write the following code inside vendor/laravel/framework/src/Illuminate/Database/Query/Builder.php in the WhereIn method after the check has been made to see whether $values is an instance of Closure (Line number 672 in my project)
if(count($values)>800)
{
return $this->whereRaw($column. ' IN ('.implode(',', $values).')');
}
i'm facing issue in xpath-I need do a check two attribute values, if the condition satisfies need to do hard code my own value. Below is my xml.
I need to check the condition like inside subroot- if ItemType=Table1 and ItemCondition=Chair1 then i have to give a hard coded value 'Proceed'( this hard coded value i will map to target side of datamapper).
<Root>
<SubRoot>
<ItemType>Table1</ItemType>
<ItemCondition>Chair1</ItemCondition>
<ItemValue>
.......
</ItemValue>
</SubRoot>
<SubRoot>
<ItemType>Table2</ItemType>
<ItemCondition>chair2</ItemCondition>
<ItemValue>
.......
</ItemValue>
</SubRoot>
....Will have multiple subroot
</Root>
I have tried to define rules as below, but it is throwing error
Type: String
Context:/Root
Xpath: substring("Proceed", 1 div boolean(/SubRoot[ItemType="Table1" and ItemCondition="Chair1"]))
But it is throwing error like
net.sf.saxon.trans.XPathException: Arithmetic operator is not defined for arguments of types (xs:integer, xs:boolean)
Is there any other shortcut way to perform this.Could you please help me, i have given lot more effort. Not able to resolve it. Thanks in advance.
I am not sure where you are applying this but the XPath expression you are looking for is:
fn:contains(/Root/SubRoot[2]/ItemCondition, "chair") and fn:contains(/Root/SubRoot[2]/ItemType, "Table")
So here is an example returning "Proceed" or "Stop" as appropriate:
if (fn:contains(/Root/SubRoot[1]/ItemCondition, "Chair") and fn:contains(/Root/SubRoot[2]/ItemType, "Table")) then 'Proceed' else 'Stop'
To implement the above condition , i was initially tired to do in xpath, gave me lot of error. I have implemented by simple if else condition in script part of data mapper
if ( (input.ItemType == 'Table') and (input.ItemCondition == 'chair')) {
output.Item = 'Proceed'}
else {
output.Item = 'Stop '};
Make sure about your precedence. Example, Here in the xml structure( or converted POJO) ItemType has to be checked first then followed with ItemCondition.
&& not seems to be working for me, change to 'and' operator
If you were first time trying to implement the logic. It may help you.