Entity Framework, update multiple fields more efficiently - sql

Question

Using Entity Framework, I am updating about 300 rows, and 9 columns about every 30 seconds. Below is how I am currently doing it. My question is, how can I make the code more efficient?
Every once in a while, I feel my database gets hit with the impact and I just want to make it as efficient as possible.
// FOREACH OF MY 300 ROWS
var original = db.MarketDatas.FirstOrDefault(x => x.BBSymbol == targetBBsymbol);
if (original != null)
{
//if (original.BBSymbol.ToUpper() == "NOH7 INDEX")
//{
// var x1 = 1;
//}
original.last_price = marketDataItem.last_price;
original.bid = marketDataItem.bid;
original.ask = marketDataItem.ask;
if (marketDataItem.px_settle_last_dt_rt != null)
{
original.px_settle_last_dt_rt = marketDataItem.px_settle_last_dt_rt;
}
if (marketDataItem.px_settle_actual_rt != 0)
{
original.px_settle_actual_rt = marketDataItem.px_settle_actual_rt;
}
original.chg_on_day = marketDataItem.chg_on_day;
if (marketDataItem.prev_close_value_realtime != 0)
{
original.prev_close_value_realtime = marketDataItem.prev_close_value_realtime;
}
if (marketDataItem.px_settle_last_dt_rt != null)
{
DateTime d2 = (DateTime)marketDataItem.px_settle_last_dt_rt;
if (d1.Day == d2.Day)
{
//market has settled
original.settled = "yes";
}
else
{
//market has NOT settled
original.settled = "no";
}
}
if (marketDataItem.updateTime.Year != 1)
{
original.updateTime = marketDataItem.updateTime;
}
db.SaveChanges();
}
Watching what is being hit in the debugger...
SELECT TOP (1)
[Extent1].[MarketDataID] AS [MarketDataID],
[Extent1].[BBSymbol] AS [BBSymbol],
[Extent1].[Name] AS [Name],
[Extent1].[fut_Val_Pt] AS [fut_Val_Pt],
[Extent1].[crncy] AS [crncy],
[Extent1].[fut_tick_size] AS [fut_tick_size],
[Extent1].[fut_tick_val] AS [fut_tick_val],
[Extent1].[fut_init_spec_ml] AS [fut_init_spec_ml],
[Extent1].[last_price] AS [last_price],
[Extent1].[bid] AS [bid],
[Extent1].[ask] AS [ask],
[Extent1].[px_settle_last_dt_rt] AS [px_settle_last_dt_rt],
[Extent1].[px_settle_actual_rt] AS [px_settle_actual_rt],
[Extent1].[settled] AS [settled],
[Extent1].[chg_on_day] AS [chg_on_day],
[Extent1].[prev_close_value_realtime] AS [prev_close_value_realtime],
[Extent1].[last_tradeable_dt] AS [last_tradeable_dt],
[Extent1].[fut_notice_first] AS [fut_notice_first],
[Extent1].[updateTime] AS [updateTime]
FROM [dbo].[MarketDatas] AS [Extent1]
WHERE ([Extent1].[BBSymbol] = #p__linq__0) OR (([Extent1].[BBSymbol] IS NULL) AND (#p__linq__0 IS NULL))
It seems it updates the same thing multiple times, if I am understanding it correctly.
UPDATE [dbo].[MarketDatas]
SET [last_price] = #0, [chg_on_day] = #1, [updateTime] = #2
WHERE ([MarketDataID] = #3)
UPDATE [dbo].[MarketDatas]
SET [last_price] = #0, [chg_on_day] = #1, [updateTime] = #2
WHERE ([MarketDataID] = #3)

Answer 1

You can reduce this to 2 round trips.
Don't call SaveChanges() in side the loop. Move it outside and call it after you are done processing everything.
Write the select in such a way that it retrieves all the originals in one go and pushes them to a memory collection, then retrieve from that for each item you are updating/inserting.
code
// use this as your source
// to retrieve an item later use TryGetValue
var originals = db.MarketDatas
.Where(x => arrayOftargetBBsymbol.Contains(x.BBSymbol));
.ToDictionary(x => x.BBSymbol, y => y);
// iterate over changes you want to make
foreach(var change in changes){
MarketData original = null;
// is there an existing entity
if(originals.TryGetValue(change.targetBBsymbol, out original)){
// update your original
}
}
// save changes all at once
db.SaveChanges();

Answer 2

You could only execute "db.SaveChanges" after your foreach loop. It think it you would do exactly what your are asking for.

Answer 3

It seems it updates the same thing multiple times, if I am
understanding it correctly.
Entity Framework performs a database round-trip for every entity to update.
Just check the parameter value, they will be different.
how can I make the code more efficient
The major problem is your current solution is not scalable.
It works well when you only have a few entities to update but will become worse and worse are the number of items to update in a batch will increase.
It's often better to make this kind of logic all in the database, but perhaps you cannot do it.
Disclaimer: I'm the owner of the project Entity Framework Extensions
This library can make your code more efficient by allowing you to save multiples entities at once. All bulk operations are supported:
BulkSaveChanges
BulkInsert
BulkUpdate
BulkDelete
BulkMerge
BulkSynchronize
Example:
// Easy to use
context.BulkSaveChanges();
// Easy to customize
context.BulkSaveChanges(bulk => bulk.BatchSize = 100);
// Perform Bulk Operations
context.BulkDelete(customers);
context.BulkInsert(customers);
context.BulkUpdate(customers);
// Customize Primary Key
context.BulkMerge(customers, operation => {
operation.ColumnPrimaryKeyExpression =
customer => customer.Code;
});