Tag: SQL Server

Full Text Search, SQL

CONTAINSTABLE is not returning records from full text enabled table in SQL Server

Recently, we have an issue, FULL TEXT search was not working with CONTIANSTABLE. My friend was searching for a word in a document where the table is enabled with FULL TEXT feature, however the search was not bringing any records.

My first thought was there could be a missing join condition that could not get the results. The actual query in the issue was really a big one with lots of tables and filters involved.So the first thing that we did remove all joins or conditions and see if CONTAINSTABLE works good, but that attempt was also failing. It was a clear indication that there is something wrong that it could not return results at FULL TEXT functionality.

For everyone to understand better, Let us go through a sample script to replicate the issue:

1. Create a table for our example

CREATE TABLE [DBO].[DOCUMENTTABLE](
	[DOCUMENTID] [UNIQUEIDENTIFIER] NOT NULL,
	[DOCUMENT_CONTENT] [IMAGE] NULL
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

CREATE INDEX IX_DOCUMENTTABLE ON DOCUMETTABLE(DOCUMENTID)

2. Load some data into Table – We uploaded the same file in question which is a .xlsx type

3. Query table with CONTAINSTABLE

Select * From CONTAINSTABLE (DocumentTable, DOCUMENT_CONTENT,'reporting')

Msg 7601, Level 16, State 2, Line 2
Cannot use a CONTAINS or FREETEXT predicate on table or indexed view ‘DocumentTable’ because it is not full-text indexed.

4. Enable FULL TEXT Indexing on the table

5. While executing the query, it is observed again no data returned

Further, we decided to check the document and its content for the search word manually and found the word was present and the document was also the same “.xlsx”. It is to be noted that we saved the data in an IMAGE datatype as shown in the example. With that information, we wanted to know the supporting file types in our full text enabled table with the below query.

select document_type, path from sys.fulltext_document_types

The above query was not returning the document type – “.xlsx” and it clearly indicated that the reason why the document could not search the word as the document type was a non-supporting one. [DOCUMENTTABLE] is a table that enabled FULL TEXT and the datatype of the field “[DOCUMENT_CONTENT]” was IMAGE. Then, my analysis took me a very important information that if we need to index a document type for which a pre-installed iFilter does not exists at OS level, we need to install the appropriate iFilter in the OS and then load those into SQL Server for a successful search functionality.

How to install the iFilter and Load into SQL Server

1. Download the iFilter , the below supports a wide range of document types

Microsoft Office 2010 Filter Packs

(Please note that MSmight retire the above as latest version is released, you may need to check for the latest.)

The following file types are supported by the Office 2010 Filter Pack:

2. Install the downloaded set

3. Load the installed OS resources to SQL Server as below.

exec sp_fulltext_service 'load_os_resources', 1;
exec sp_fulltext_service 'verify_signature', 0;
exec sp_fulltext_service 'Update_languages'
exec sp_fulltext_service 'Restart_all_fdhosts'

Once the above steps are completed, we were able to query the word and the results were returned as expected.

Hope this helps you in a similar situation and it was a good lesson learned to me!

References:
How to register iFilters

Change Data Capture, Errors and Exceptions, SQL

Could not update the metadata that indicates database <> is enabled for Change Data Capture. The failure occurred when executing the command ‘SetCDCTracked(Value = 1)’. The error returned was 15517: ‘Cannot execute as the database principal because the principal “dbo” does not exist, this type of principal cannot be impersonated, or you do not have permission.’. Use the action and error to determine the cause of the failure and resubmit the request.

While configuring Change Data Capture on a database that is restored from different environment, we might end up with an error message as below:

Could not update the metadata that indicates database <> is enabled for Change Data Capture. The failure occurred when executing the command ‘SetCDCTracked(Value = 1)’. The error returned was 15517: ‘Cannot execute as the database principal because the principal “dbo” does not exist, this type of principal cannot be impersonated, or you do not have permission.’. Use the action and error to determine the cause of the failure and resubmit the request.

To resolve the issue, we need to change the owner of database and then enable CDC for the database as below. Please note that, the database would have restored irrespective of the error. You just have to run the below statement to avoid similar issues in future.

EXEC sp_changedbowner 'sa'
EXEC sys.sp_cdc_enable_db ;

Ref: https://docs.microsoft.com/en-us/sql/relational-databases/system-stored-procedures/sp-changedbowner-transact-sql?view=sql-server-2017

DBA Utilities, Errors and Exceptions, SCRIPT GALLERY, SQL

Decoding hexa error code to windows error message in SQL Server

Problem Statement:
Sometimes, the error messages generated are not friendly to understand the underlined issues. This is going to be an extra effort to google out for most of us with the error code (mostly a hexa value) and identify the corresponding windows error message.

Solution:
A simple solution would be to use NET HELPMSG with the errocode. But if the error code is a hexa value, then we need to identify the corresponding Decimal value to use as a parameter to NET HELPMSG.

Here is a script to identify actual error message from hex error code. This is important to be aware that this approach will only work for Win32 error codes from Microsoft Windows. If the net helpmsg command does not return a result, the cause is likely the error has not originated from Windows, or no longer a valid Win32 process.

DECLARE @hex VARCHAR(64) = '0x80070643'
Set @hex = Right(@hex,4)

DECLARE @rez BIGINT;
SELECT @rez = ISNULL(@rez,0) * 16 + 
CHARINDEX(substring(@hex,n.number+1,1),'0123456789ABCDEF') - 1
FROM MASTER..spt_values n WHERE n.TYPE='P' AND n.number<len(@hex)

/*
	--To use NET HELPMSG, need to enable xp_cmdshell as below:

	EXEC sp_configure 'show advanced options',1
	RECONFIGURE WITH OVERRIDE
	EXEC sp_configure 'xp_cmdshell',1
	RECONFIGURE WITH OVERRIDE
	EXEC sp_configure 'show advanced options',0
	RECONFIGURE WITH OVERRIDE
*/

Declare @Table Table(WindowsErrorMessage nVarchar(MAX))
Declare @s nvarchar(500) = 'NET HELPMSG ' + Cast(@rez as varchar(MAX))
Insert into @Table 
exec xp_cmdshell @s

Select @hex HexaVal,@rez DecimalVal,* From @Table 
where WindowsErrorMessage is not null
Cached Plan Analysis, SQL, Wait types

How to identify parallel plans in SQL Server
Few years back, on one of my engagements, identified lots of performance issues with an application. As part of a detailed analysis, it is observed there are lots of queries under performing with wait type “CXPACKET”. In short, CXPACKET wait types are involved in parallel query execution. These wait types indicate that the SPID is waiting on a parallel process to complete or start. There are many reasons your query may undergo a parallel execution like missing index, non optimized sql script etc. But, CXPACKET is not ALWAYS a bad thing.We will see about CXPACKET in detail with another post.

Now, We will see how to identify the queries with parallel execution. Once you identified the queries, you can further examine to identify the actual cause of the issues and optimize.

Script

select p.*,q.*,cp.plan_handle
from sys.dm_exec_cached_plans cp
cross apply sys.dm_exec_query_plan(cp.plan_handle) p
cross apply sys.dm_exec_sql_text(cp.plan_handle) as q
where
cp.cacheobjtype = 'Compiled Plan' and
p.query_plan.value('declare namespace
p="http://schemas.microsoft.com/sqlserver/2004/07/showplan";
max(//p:RelOp/@Parallel)', 'float') > 0

Please note that the above query gets information from cached plan in SQL Server. Hence, I will recommend to run a load test with a real time workload and use the script to identify the parallel executing queries. It is also important that the cached plans may get flushed due various factors like memory pressure, recompile of procedures, auto stats updates etc. But, this helped me a lot at times!!!

[Edit – 8th-Sep-202]

How do we know the degree of parallelism of a currently running query?

select session_id, scheduler_id
from sys.dm_os_tasks
where parent_task_address IS NOT NULL
--AND session_id = ? --You can uncomment and give spid as required.

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