I need select from tarantool all datat by two values from one space.
How i can perform request to tarantool like in mysql?
select from aaa where a=1a22cadbdb or a=7f626e0123
Now i can make two requests:
box.space.logs:select({'1a22cadbdb'})
box.space.logs:select({'7f626e0123'})
but i don't know how to merge result into one ;(
Following code merge field[0] to lua table
a = box.space.logs:select({'1a22cadbdb'})
b = box.space.logs:select({'7f626e0123'})
c = { field_1 = a[0], field_2 = b[0] }
The select return tuple or tuples so you can extract value via [].
More details about select: http://tarantool.org/doc/book/box/box_index.html?highlight=select#lua-function.index_object.select
More details about tuple: http://tarantool.org/doc/book/box/box_tuple.html?highlight=tuple#lua-module.box.tuple
Nowadays Tarantool allows you to retrieve via SQL, for example box.execute([[select from "aaa" where "a"='1a22cadbdb' or "a"='7f626e0123';]]). You have to add the field names and types of aaa before doing this, with the format() function.
For me this work fine, but need make check for return from first select:
local res = {}
for k, v in pairs (box.space.email:select({email})[1]) do
if type(v) == 'string' then
table.insert(res, box.space.logs:select({v})[1])
end
end
Related
provied that there's a Map like,,,
map.text
[key1#v1]
[key2#v2]
[key3#v3]
then, if I try to find 'value of 'key2'',
A = load ‘map.text’ as (M:map[]);
B = foreach A generate M#'key2';
C = filter B by $0!=''; // to get rid of empty value like (), (), ().
dump C;
is there any other way to find key2? with using 'filter by' only.
thxs ya.
There is no need to GENERATE a field and then use it in a FILTER; you can include it in the FILTER statement to begin with:
A = load 'map.text' as (M:map[]);
B = filter A by M#'key2' != '';
dump B;
On your data, this returns one record:
([key2#v2])
As a side note, in case empty strings are ever valid values, the criterion you might rather use is by M#'key2' is not null.
I am trying to select some records using LINQ for Entities (EF4 Code First).
I have a table called Monitoring with a field called AnimalType which has values such as
"Lion,Tiger,Goat"
"Snake,Lion,Horse"
"Rattlesnake"
"Mountain Lion"
I want to pass in some values in a string array (animalValues) and have the rows returned from the Monitorings table where one or more values in the field AnimalType match the one or more values from the animalValues. The following code ALMOST works as I wanted but I've discovered a major flaw with the approach I've taken.
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
var result = from m in db.Monitorings
where animalValues.Any(c => m.AnimalType.Contains(c))
select m;
return result;
}
To explain the problem, if I pass in animalValues = { "Lion", "Tiger" } I find that three rows are selected due to the fact that the 4th record "Mountain Lion" contains the word "Lion" which it regards as a match.
This isn't what I wanted to happen. I need "Lion" to only match "Lion" and not "Mountain Lion".
Another example is if I pass in "Snake" I get rows which include "Rattlesnake". I'm hoping somebody has a better bit of LINQ code that will allow for matches that match the exact comma delimited value and not just a part of it as in "Snake" matching "Rattlesnake".
This is a kind of hack that will do the work:
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
var values = animalValues.Select(x => "," + x + ",");
var result = from m in db.Monitorings
where values.Any(c => ("," + m.AnimalType + ",").Contains(c))
select m;
return result;
}
This way, you will have
",Lion,Tiger,Goat,"
",Snake,Lion,Horse,"
",Rattlesnake,"
",Mountain Lion,"
And check for ",Lion," and "Mountain Lion" won't match.
It's dirty, I know.
Because the data in your field is comma delimited you really need to break those entries up individually. Since SQL doesn't really support a way to split strings, the option that I've come up with is to execute two queries.
The first query uses the code you started with to at least get you in the ballpark and minimize the amount of data you're retrieving. It converts it to a List<> to actually execute the query and bring the results into memory which will allow access to more extension methods like Split().
The second query uses the subset of data in memory and joins it with your database table to then pull out the exact matches:
public IQueryable<Monitoring> GetMonitoringList(string[] animalValues)
{
// execute a query that is greedy in its matches, but at least
// it's still only a subset of data. The ToList()
// brings the data into memory, so to speak
var subsetData = (from m in db.Monitorings
where animalValues.Any(c => m.AnimalType.Contains(c))
select m).ToList();
// given that subset of data in the List<>, join it against the DB again
// and get the exact matches this time
var result = from data in subsetData
join m in db.Monitorings on data.ID equals m.ID
where data.AnimalType.Split(',').Intersect(animalValues).Any ()
select m;
return result;
}
So I have a list(table) of about 100k items and I want to retrieve all values that match a given list.
I have something like this.
the Table Sections key is NOT a primary key, so I'm expecting each value in listOfKeys to return a few rows.
List<int> listOfKeys = new List<int>(){1,3,44};
var allSections = Sections.Where(s => listOfKeys.Contains(s.id));
I don't know if it makes a difference but generally listOfKeys will only have between 1 to 3 items.
I'm using the Entity Framework.
So my question is, is this the best / fastest way to include a list in a linq expression?
I'm assuming that it isn't better to use another .NETICollection data object. Should I be using a Union or something?
Thanks
Suppose the listOfKeys will contain only small about of items and it's local list (not from database), like <50, then it's OK. The query generated will be basically WHERE id in (...) or WHERE id = ... OR id = ... ... and that's OK for database engine to handle it.
A Join would probably be more efficient:
var allSections =
from s in Sections
join k in listOfKeys on s.id equals k
select s;
Or, if you prefer the extension method syntax:
var allSections = Sections.Join(listOfKeys, s => s.id, k => k, (s, k) => s);
In the Sequel ORM for Ruby, the Dataset class has an all method which produces an Array of row hashes: each row is a Hash with column names as keys.
For example, given a table T:
a b c
--------------
0 22 "Abe"
1 35 "Betty"
2 58 "Chris"
then:
ds = DB['select a, b, c from T']
ah = ds.all # Array of row Hashes
should produce:
[{"a":0,"b":22,"c":"Abe"},{"a":1,"b":35,"c":"Betty"},{"a":2,"b":58,"c":"Chris"}]
Is there a way built in to Sequel to instead produce an Array of row Arrays, where each row is an array of only the values in each row in the order specified in the query? Sort of how select_rows works in ActiveRecord? Something like this:
aa = ds.rows # Array of row Arrays
which would produce:
[[0,22,"Abe"],[1,35,"Betty"],[2,58,"Chris"]]
Note: the expression:
aa = ds.map { |h| h.values }
produces an array of arrays, but the order of values in the rows is NOT guaranteed to match the order requested in the original query. In this example, aa might look like:
[["Abe",0,22],["Betty",1,35],["Chris",2,58]]
Old versions of Sequel (pre 2.0) had the ability in some adapters to return arrays instead of hashes. But it caused numerous issues, nobody used it, and I didn't want to maintain it, so it was removed. If you really want arrays, you need to drop down to the connection level and use a connection specific method:
DB.synchronize do |conn|
rows = conn.exec('SQL Here') # Hypothetical example code
end
The actual code you need will depend on the adapter you are using.
DB[:table].where().select_map(:id)
If you want just an array of array of values...
DB['select * from T'].map { |h| h.values }
seems to work
UPDATE given the updated requirement of the column order matching the query order...
cols= [:a, :c, :b]
DB[:T].select{cols}.collect{ |h| cols.collect {|c| h[c]}}
not very pretty but guaranteed order is the same as the select order.
There does not appear to be a builtin to do this.
You could make a request for the feature.
I haven't yet found a built-in method to return an array of row arrays where the values in the row arrays are ordered by the column order in the original query. The following function does* although I suspect an internal method could be more effecient:
def rows( ds )
ret = []
column_keys = ds.columns # guaranteed to match query order?
ds.all { |row_hash|
row_array = []
column_keys.map { |column_key| row_array << row_hash[column_key] }
ret << row_array
}
ret
end
*This function depends on the order of the array returned by Dataset.columns. If this order is undefined, then this rows function isn't very useful.
have you tried this?
ds = DB['select a, b, c from T'].to_a
not sure it it works but give it a shot.
Can anybody tell me how I would get the records in the first statement that are not in the second statement (see below)?
from or in TblOrganisations
where or.OrgType == 2
select or.PkOrgID
Second query:
from o in TblOrganisations
join m in LuMetricSites
on o.PkOrgID equals m.FkSiteID
orderby m.SiteOrder
select o.PkOrgID
If you only need the IDs then Except should do the trick:
var inFirstButNotInSecond = first.Except(second);
Note that Except treats the two sequences as sets. This means that any duplicate elements in first won't be included in the results. I suspect that this won't be a problem since the name PkOrgID suggests a unique ID of some kind.
(See the documentation for Enumerable.Except and Queryable.Except for more info.)
Do you need the whole records, or just the IDs? The IDs are easy...
var ids = firstQuery.Except(secondQuery);
EDIT: Okay, if you can't do that, you'll need something like:
var secondQuery = ...; // As you've already got it
var query = from or in TblOrganisations
where or.OrgType == 2
where !secondQuery.Contains(or.PkOrgID)
select ...;
Check the SQL it produces, but I think it should do the right thing. Note that there's no point in performing any ordering in the second query - or even the join against TblOrganisations. In other words, you could use:
var query = from or in TblOrganisations
where or.OrgType == 2
where !LuMetricSites.Select(m => m.FkSiteID).Contains(or.PkOrgID)
select ...;
Use Except:
var filtered = first.Except(second);