Hi, folks!

Suppose you have a Caché class with %String property which contains relatively large text (from 10 to 2000 symbols).

The class:

Class Test.Duplicates Extends %Persistent 

{

Property Text As %String (MAXLEN = 2000);

}

And you have thousands of entries.

What are the best options to find entries which are duplicates on this property?

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Hi,

I have a class with around 400k lines and 60 columns. Class storage is Cache SQL storage (Mapped from a global).

 I want to create multiple indices on certain fields.

I am familiar with two approaches:

1. Create a new map (Index type) on a pointer global.

2. Create a bitmap index

Which approach is more recommended to be used in the case I described? If there are any other approaches, I will be happy to hear.

Thanks :)

 

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Have some free text fields in your application that you wish you could search efficiently?  Tried using some methods before but found out that they just cannot match the performance needs of your customers?  Do I have one weird trick that will solve all your problems?  Don’t you already know!?  All I do is bring great solutions to your performance pitfalls!

As usual, if you want the TL;DR (too long; didn’t read) version, skip to the end.  Just know you are hurting my feelings.

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2 11 1,898

Overview

Encryption of sensitive data becomes more and more important for applications. For example patient names, SSN, address-data or credit card-numbers etc..

Cache supports different flavors of encryption. Block-level database encryption and data-element encryption. The block-level database encryption protects an entire database.  The decryption/encryption is done when a block is written/read to or from the database and has very little impact on the performance.

With data-element encryption only certain data-fields are encrypted.  Fields that contain sensitive data like patient data or credit-card numbers. Data-element encryption is also useful if a re-encryption is required periodically. With data-element encryption it is the responsibility of the application to encrypt/decrypt the data.

Both encryption methods leverage the managed key encryption infrastructure of Caché.

The following article describes a sample use-case where data-element encryption is used to encrypt person data.  

But what if you have hundreds of thousands of records with an encrypted datafield and you have the need to search that field? Decryption of the field-values prior to the search is not an option. What about indices?

This article describes a possible solution and develops step-by-step a small example how you can use SQL and indices to search encrypted fields. 

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Question
David Foard · Dec 26, 2019
Performant index on date field

Is there a way to get a good performing index on a date field? I have tried various date property indexes and the query plan is always in a pretty high range. Below are query plan result values I have observed:

   StartDate > '2019-12-01'  --cost = 699168
   StartDate = '2019-12-21'  --cost 70666
   StartDate between '2019-12-21' and '2019-21-28' --cost = 492058

 

The query plans above were for type %TimeStamp.

 

 


 

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I'm using Cache SQL and want the ability to choose a specific index.

I've boiled the problem down to one table and simplified the query down to

SELECT *
FROM Registration.PatResp
WHERE SchedApptNum=8450022

 

SchedApptNum is indexed, but instead of using that column, "Show Plan" indicates that it's looping through the entire Registration.PatResp table on Id (the primary key for the table).

I've done a tune-table with no change.

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Hi!

Consider I have a class Package.Data with Property UniqueStringValue as %String.

I introduced the Index for this property:

 Index ValueIndex on UniqueStringValue [Unique];

It works well.  But if I try to check if there is an object with the certain value in code like this:

if ##class(Package.Data).ValueIndexExists(value)  

this expression fails, if value="value", even if there is an instance with instance.UniqueStingValue="Value"

How can I set the index to prevent saving case sensitive values in this class?

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Our team is reworking an application to use REST services that use the same database as our current ZEN application. One of the new REST endpoints uses a query that ran very slowly when first implemented. After some analysis, we found that an index on one of the fields in the table greatly improved performance (a query that took 35 seconds was now taking a fraction of a second).

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Hi,

I am new to Cache' MV but have extensive experience with other Pick flavors especially Unidata. 

I need to determine the impact of adding several indexes to a large file with over 51,000,000 records. 

On other systems, I could use FILE.STAT, ANALYZE.FILE and shell to the OS to determine how large the index file was. 

None of those seem to be available in Cache' MV. Shelling to the OS just tells me the size of CACHE.DAT.

What is the best way to determine what the disk impact would be if I added an index (CREATE-INDEX) to a file?

TIA,

Steve

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Question
Neerav Adam Verma · Mar 5, 2019
PrimaryKey vs Idkey

Just wondering an Insight in the difference between these two indexes

IdKey / PrimaryKey
================= 

Property Identifier As %Integer

Index Index1 on Identifier [Idkey]

Index Index2 on Identifier [PrimaryKey]

What's the difference?

1. If I don't have Index1 and only have Index2,  then cache does still make its own id.
So how and why  do I ever use the PrimaryKey.  In Joins ??

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Hi guys!


Unique, PrimaryKey and IDKey?
In what contexts does it apply?

IDKey sets the registry key access to the store.
PrimaryKey, Unique, and IDKey define the uniqueness in the records, but what is correct?

I use everyone? What is the context of each?

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0 4 452
Question
Andy Richards · Jun 1, 2016
Activating an index

I have a production system that has a large dataset of about 2 million rows. I need to create an index on a property but don't want it available to queries until the index is fully populated. Is there a way I can create the indexed, fire off the build, then "activate" the index so queries can use it.

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0 3 302
Question
Alexandr Ladoshkin · Nov 23, 2017
Indexing null value

Dear community!

I have problem with index NULL value.  Unique index doesn't work for this case.  If I use insert and one of parameter is "NULL". Message of constraint doesn't appear and row is inserted into table successfully.  How Can I use index with NULL?

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Article
Robert Cemper · Apr 26, 2020 5m read
Materialized Views

A VIEW in SQL is basically a prepared SQL statement.
It has to be executed and assembled like any other SQL query.
MATERIALIZED VIEW means that the content is collected before hands and can be retrieved rather fast.
I saw the concept first with my favorite competitor named O* and they made a lot of noise about it.

  { favorite: because I could win every benchmark against them devil }

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In the previous parts (1, 2) we talked about globals as trees. In this article, we will look at them as sparse arrays.

A sparse array - is a type of array where most values assume an identical value.

In practice, you will often see sparse arrays so huge that there is no point in occupying memory with identical elements. Therefore, it makes sense to organize sparse arrays in such a way that memory is not wasted on storing duplicate values.

In some programming languages, sparse arrays are part of the language - for example, in J, MATLAB. In other languages, there are special libraries that let you use them. For C++, those would be Eigen and the like.

Globals are good candidates for implementing sparse arrays for the following reasons:

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Hi,

I know of the existance of (ELEMENTS) to create an index from a list, but I actually would like to index the content of an element of a list. Is it possible?

 

My scenario:

Class:
Property Test As list of TestList;
 

Test.List:
Property Name As %String;
Property Surname As %String;

I would like to have an  index based on the TestList.Name. If I try using

Index NewIndex On Test(ELEMENTS)

it will create an index with Name and Surname in it, but I just want to have an index with the name. Is it possible? 

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Hello Fellow Cache Developers:  

Has anyone ever created an index on values of a list property?   If so, would you be willing to share an example?

Also, feel free to offer input and suggestions regarding use of indexes on List values.

Here is my database scenario:

Parent Class:

PropertyA - %String  

PropertyB - %Integer 

Child Class:

PropertyC - %Integer

PropertyD - list of %Integer

Data illustration:

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I have a class which defines a property as array of %String. Is it possible to index values of this property and use this property in SQL?

I have tried 'Index idx On prop(ELEMENTS)' and then a select from the generated collection table, but this is still orders of magnitude slower than queries to the containing class.

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Question
Kenneth Poindexter · Apr 15, 2018
Indexes in Cache Objects

Hi-

I have the following objects

Class A

   Property P1 As B

   Property P2 As %String

   Property P3 As %String

Class B

   Property P1 As %String

Can I create an index in Class A based on P1.P1.  Basically I want an index of class A by property P1 in class B

I tried creating the following but got a compile error

Index I1 On P1.P1

Thanks

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I have a persistent class that represents cities across the United States.  It is below, but basically has a City Id, Name, Lat, Lon and a few other unimportant fields for this issue.  Anytime I attempt to query on the Latitude or Longitude it immediately returns no results.  My first thought was that it was a casting issue so I tried casting both sides to floats, ints, even strings and in all cases it immediately comes back with no results.  I then decided to cast it to a string and attempt a like statement thinking it might be something about how floats are handled, but still no joy.  Any

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Question
Paul Riker · Mar 29, 2019
Ensemble as a Data lake

We have been storing raw messages in a MySQL database for DR and ad hoc purposes. We are thinking of using an Ensemble instance as our data lake instead. We could segregate the source data by namespace or by global. But either way we'll want a custom global to index the data for data retrieval performance purposes.

Anyone else taking this approach? Any feedback?

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The object and relational data models of the Caché database support three types of indexes, which are standard, bitmap, and bitslice. In addition to these three native types, developers can declare their own custom types of indexes and use them in any classes since version 2013.1. For example, iFind text indexes use that mechanism.

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Hello, community!

I've stumbled on some unexpected behavior, and decided to check with you if this is normal. Basically, I'm rebuilding indices and the result is not journaling (which leads to missing indices at shadow server).

The $ZV is "Cache for UNIX (Red Hat Enterprise Linux for x86-64) 2015.2.1 (Build 705U) Mon Aug 31 2015 16:53:38 EDT"

I have an example class 

Class tmp.A As %Persistent;

Index IP1 On P1;

Property P1 As %String;

for example there is one object which have P1 = 1, so

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