Database Administrators Stack Exchange
Database Administrators Stack Exchange

Questions tagged [scan]

21 questions
7
votes
1 answer

STATISTICS IO for parallel index scan

Assume that there is a table with clustered index create table [a_table] ([key] binary(900) unique clustered); and some data insert into [a_table] ([key]) select top (1000000) row_number() over (order by @@spid) from sys.all_columns a cross join…
i-one
  • 2,374
  • 2
  • 14
  • 23
4
votes
1 answer

Number of full table scans

I would like to see information on how many times has a table been fully scanned. I was hoping for something like sys.dm_db_index_usage_stats but for table scans. There is a method described at the blog keepitsimleandfast, but I would rather get all…
dreptak
  • 153
  • 6
3
votes
1 answer

Is there a direct way to know if a merry-go-round scan happened?

In the docs it says we can share index scans (Advanced Scanning). Now here they used wait stats and statistics and i did not find an extended events session that could directly identify it. The question is - how can i know that an advanced scan has…
Suleyman Essa
  • 167
  • 1
  • 8
3
votes
2 answers

PostgreSQL select from table (without ORDER BY) comes out in different order every time

I have a modestly big table of about a million rows. With static where clauses it filters down to 200,000 rows. With a typical user search criterion it delivers about 100 rows. This is for a web service hit millions of times per hour. I want to keep…
Gunther Schadow
  • 523
  • 4
  • 10
3
votes
2 answers

How does a column-oriented DBMS filter on multiple columns?

I'm learning how column-oriented DBMS / "columnars" work for OLAP situations. Let's say we have a log of millions of transactions with 3 columns: timestamp, shop, product, and we want to know the products sold in the shop A in a certain time…
Basj
  • 171
  • 1
  • 7
3
votes
1 answer

Very high (99%) insertion cost in estimated execution plan

I have four tables with 500,000 to 4,000,000 rows. The script joins them and insert into a temporary table with some where clause. It is taking long. The execution plan shows 99% cost only for the insert whereas there are multiple scans in the plan.…
Som
  • 31
  • 1
  • 2
2
votes
1 answer

Vulnerability in Server from SQL Server 2008 R2

We scanned our systems and got a high vulnerability reported in a server. One of the thing that got flagged was MS12-060, which is related to MS Office 2003 Web Components that gets installed along with Analysis Services. Can we remove that…
Vijaya
  • 69
  • 2
  • 10
1
vote
2 answers

When is a regular index scan faster than a bitmap index + heap scan in Postgres?

So as far as I understand, with a regular index scan (not index-only scan), Postgres will read the index and immediately fetch the referenced rows from the heap. For a bitmap index scan + bitmap heap scan (which I will just call bitmap scan, taken…
JanKanis
  • 121
  • 5
1
vote
1 answer

How do I bulk export data from an RDBMS without killing performance?

I'm building an app that lets the user export their data. When they click the Export button, we need to do a SELECT * WHERE user_id =, save it to a CSV file, and download it. There may be hundreds of thousands of entries. If the user edits their…
Kartick Vaddadi
  • 113
  • 4
1
vote
2 answers

How to connect to Oracle RAC from HOST

For a college project, I have to set up a RAC Instance and an application, I already managed to configure my RAC lab by using virtual machines by using this video guide, now I just need to program an application to connect to my RAC instance but...…
Jeremy
  • 113
  • 5
1
vote
1 answer

Bitmap Heapscan is slow

I have 2 tables: mailings and form_responses. The form_responses table has a foreign key with the mailings table, so a mailing has one-to-many form_responses. What I want to do is calculate mailing stats: per mailing get total form_responses and…
Peter Van 't Zand
  • 13
  • 1
  • 4
1
vote
2 answers

Delete cascade produce scan intead of index seek

I have two tables in my database. TableA : 1427877 rows TableB : 339939000 rows TableB has a foreignkey column in TableB (TableB.foreignId). It has Delete On Cascade ON. The problem is when I delete a row in TableA. DELETE TableA WHERE id =…
Serafín
  • 45
  • 6
1
vote
0 answers

Performance issue in 12c - Additional Full table scan after index range scan

I am trying to improve the performance of a procedure which we recently moved from 11g to 12c. I am simply using a refcursor which gets the result set from an underlying query. In 12c I am having a significant performance hit. The query running time…
Abegin
  • 11
  • 2
1
vote
1 answer

Connect to Oracle RAC from SQL Developer?

We have set up RAC database on server. We can connect to database from sqlplus on the server using SCAN address. However, if I try to connect to RAC using SQL developer from client machine using SCAN address-based TNS entry, it shows the…
babuuz
  • 71
  • 3
  • 10
1
vote
1 answer

SCAN listener redirects connection to another port

I have setup RAC. I have two listeners LISTENER and LISTENER_DG. LISTENER is listening port 1521 LISTENER_DG is listening 1530 When client connects to the database using SHARED connection mode even indicating port 1521 during connection, scan…
kupa
  • 1,737
  • 14
  • 39
  • 55
1
2