I have a Table full of players. Each of these players can have a list of Items that they own. What I need to do is store that list of items for each player. Each item has an ID which is unique.
What I want to do is store an array of these items as a field in the Player Table. Does anyone know how this could be accomplished?
You can either go database route and create table of "ItemId to PlayerId" and query all items for given player by ID.
Or you can serialize data in XML/byte array using default .Net serialization and than dump it in BLOB field of "playerId to PlayerBLOB" table (XML/text can also be stored as text field - will be more readable).
You can store it as a delimited text. BUT! store it as xml instead, this will allow you to store complex weapon list and configuration in a column.
Related
My first task is to add two new columns to a table, first column stores the values of M and X fields values in a single column(as a single unit with a pipe separator) and second column stores O and Z fields values in a single column(as a single unit with a pipe separator).
second task selecting agency and external letter rating(shown in image) from drop down and after saving the form the value from fields M and X should move to N and Y and this values should be stored in table column that are created from task one, Now if we save the form the values should move to O and Z fields in forms and this should continue.
Can any one help me how to proceed with this and I don't know how to separate a column value into pieces and display on form.
Better if you propose any new method that does the same work.
Adding columns:
That's a bad idea. Concatenating values is easy; storing them into a column as well. But, then - in the next step - you have to split those values into two values (columns? rows?) to be joined to another value and produce result. Can you do it? Sure. Should you? No.
What to do? If you want to store 4 values, then add 4 columns to a table.
Alternatively, see if you can create a master-detail relationship between two tables so you'd actually create a new table (with a foreign key to existing table) with two additional columns:
one that says is value stored related to M or Y
value itself
It looks like more job to do, but - should pay off in the future.
Layout:
That really looks like a tabular form, which only supports what I previously said. You can't "dynamically" add rows (or, even if you could, that's really something you should avoid because you'd have to add (actually, display) separate items (not rows that share the same item name).
I have fields below in dynamo dB table
event_on -- string type
user_id -- number type
event name -- string type
Since this table may have multiple records for user_id and event_on is the single field which can be unique so I made it primary key and user_id as sort key
Now I want to delete the all records of a user, so My code is
response = dynamodb.delete_item(
TableName=events,
Key={
"user_id": {"N": str(userId)}
})
It throwing error
Exception occured An error occurred (ValidationException) when calling
the DeleteItem operation: The provided key element does not match the
schema
also is there anyway to delete with range
Can someone suggest me what should I have do with dynamodb table structure to make this code work
Thanks,
It sounds like you've modeled your data using a composite primary key, which means you have both a partition key and a sort key. Here's an example of what that looks like with some sample data.
In DynamoDB, the most efficient way to access items (aka "rows" in RDBMS language) is by specifying either the full primary key (getItem) or the partition key (query). If you want to search by any other attribute, you'll need to use the scan operation. Be very careful with scan, since it can be a costly way (both in performance and money) to access your data.
When it comes to deletion, you have a few options.
deleteItem - Deletes a single item in a table by primary key.
batchWriteItem - The BatchWriteItem operation puts or deletes multiple items in one or more tables. A single call to BatchWriteItem can write up to 16 MB of data, which can comprise as many as 25 put or delete requests
TimeToLive - You can utilize DynamoDBs Time To Live (TTL) feature to delete items you no longer need. Keep in mind that TTL only marks your items for deletion and actual deletion could take up to 48 hours.
In order to effectively use any of these options, you'll first need to identify which items you want to delete. Because you want to fetch using the value of the sort key alone, you have two options;
Use scan to find the items of interest. This is not ideal but is an option if you cannot change your data model.
Create a global secondary index (GSI) that swaps your partition key and sort key values. This pattern is called an inverted index. This would allow you to identify all items with a given user_id.
If you choose option 2, your data would look like this
This would allow you to fetch all item for a given user, which you could then delete using one of the methods I outlined above.
As you can see here, delete_item needs the primary key and not the sort key. You would have to do a full scan, and delete everything that contains the given sort key.
If you are created a DynamoDB table by the Primary key and sort key, you should provide both values to remove items from that table.
If the sort key was not added to the primary key on the table creation process, the record can be removed by the Primary key.
How I solved it.
Actually, I tried to not add the sort key when created the table. And I'm using indexes for sorting and getting items.
how to assign two variable like Part_url, Part_Number in a single data table.
You could use the GetRowItem Activity to assign variables to columns in your data table. While iterating the data table, use the GetRowItem activity with a specific column name like "Part_url" and an output as a new variable. Here are two screenshots showing how I assign several variables while iterating a data table using the column names in the data table and the GetRowItem activity:
I have an application written in Nodejs that needs to find ONE row based on a city name (this could just be the table's name, different cities will be categorized as different tables), and a field named "currentJobLoads" which is a number. For example, a user might want to find ONE row with the city name "Chicago" and the lowest currentJobLoads. How can I achieve this in Dynamodb without scan operations(since scan would be slower and can only read so much data before it gets terminated)? Any suggestions would be highly appreciated.
You didn't specify what your current partition key and sort key for the table are, but I'm guessing the currentJobLoads field isn't one of them. So you would need to create a Global Secondary Index on the currentJobLoads field, at which point you will be able to run query operations against that field.
Background
I'm writing an adapter for ESE to .NET and LINQ in a Google Code project called eselinq. One important function I can't seem to figure out is how to get a list of indexes defined for a table. I need to be able to list available indexes so the LINQ part can automatically determine when indexes can be used. This will allow much more efficient plans for user queries if appropriate indexes can be found.
There are two related functions for querying index information:
JetGetTableIndexInfo - get index information by tableID
JetGetIndexInfo - get index information by tableName
These only differ in how the related table is specified (name or tableid). It sounds like these would support the function I want but all the info levels seem to require that I already have a certain index to query information for. The only exception is JET_IdxInfoCount, but that only counts how many indexes are present.
JET_IdxInfo with its JET_INDEXLIST sounds plausible but it only lists the columns on a specific index.
Alternatives
I am aware that I could get the index information another way, like annotations on .NET types corresponding to database tables, or by requiring a index mapping be provided ahead of time. I think there's enough introspection implemented to make everything else work out of the box without the user supplying extra information, except for this one function.
Another option may be to examine the system tables to find related index objects, but this is would mean depending on an undocumented interface.
To satisfy this question, I want a supported method of enumerating the indexes (just the name would be sufficient) on a table.
You are correct about JetGetTableIndexInfo and JetGetIndexInfo and JET_IdxInfo. The twist is that the data is returned in a somewhat complex: a temporary table is returned containing a row for the index and then a row for each column in the table. To just get the index names you will need to skip the column rows (the column count is given by the value of the columnidcColumn column in the first row).
For a .NET example of how to decipher this, look at the ManagedEsent project. In the MetaDataHelpers.cs file there is a method called GetIndexInfoFromIndexlist that extracts all the data from the temporary table.