List:Falcon Storage Engine« Previous MessageNext Message »
From:Jim Starkey Date:January 25 2009 1:28am
Subject:Re: Quick question on row counts
View as plain text  
Keith Murphy wrote:
> Hello everyone,
>
> I have a quick question. Testing seems to indicate that Falcon keeps 
> accurate stats on the number of rows in a table. It appears similar to 
> the way MyISAM tables work.  This can shown by running a 'SHOW TABLE 
> STATUS' command and comparing the number of rows with the SELECT 
> COUNT(*) command. Am I correct in this? Or have I not done enough tests?
>
> Also, SELECT COUNT(*) appears to return a number of rows much quick 
> than a similar command on InnoDB tables. Again..similar to MyISAM. Am 
> I accurate in this?
>
The row count is Falcon is not guaranteed accurate and should not be 
depended upon.  Falcon does a good faith effort to track table 
cardinalities, but number of records visible to any given transaction is 
not necessarily the number of committed records in the table.  Other 
transaction may have committed records that are not yet visible, and 
pending transactions have have insert records that will eventually be 
rolled back.

Count(*) is accurate from a transaction's perspective, but will not 
include record insert -- even if committed -- by a concurrent transaction.

The record could from SHOW TABLE STATUS is a good faith estimate, 
nothing more.

Thread
Problems with record visibility and how it is computedOlav Sandstaa21 Jan
  • search for null values in indexed columnsVladislav Vaintroub21 Jan
    • Re: search for null values in indexed columnsLars-Erik Bjørk21 Jan
    • Re: search for null values in indexed columnsKevin Lewis21 Jan
      • RE: search for null values in indexed columnsVladislav Vaintroub21 Jan
        • Re: search for null values in indexed columnsKevin Lewis21 Jan
      • Re: search for null values in indexed columnsJames Day23 Jan
  • Re: Problems with record visibility and how it is computedOlav Sandstaa23 Jan
    • Re: Problems with record visibility and how it is computedJim Starkey23 Jan
      • Re: Problems with record visibility and how it is computedKevin Lewis28 Jan
        • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
          • Re: Problems with record visibility and how it is computedKevin Lewis28 Jan
            • Cycle Locking (was Problems with record visibility and how it iscomputed)Jim Starkey28 Jan
            • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
              • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
                • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
                  • Re: Problems with record visibility and how it is computedOlav Sandstaa26 Feb
                    • New Transaction State object (Was: Problems with record visibility andhow it is computed)Olav Sandstaa16 Mar
                      • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Kevin Lewis16 Mar
                      • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey16 Mar
                        • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Olav Sandstaa19 Mar
                          • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey19 Mar
                            • RE: New Transaction State object (Was: Problems with record visibilityand how it is computed)Vladislav Vaintroub20 Mar
                            • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Olav Sandstaa20 Mar
                              • Re: New Transaction State object (Was: Problems with record visibilityand how it is computed)Jim Starkey20 Mar
          • Re: Problems with record visibility and how it is computedOlav Sandstaa28 Jan
            • Re: Problems with record visibility and how it is computedJim Starkey28 Jan
              • Another Idea for Transaction Lifetime ControlJim Starkey28 Jan
                • Re: Another Idea for Transaction Lifetime ControlJim Starkey29 Jan
              • RE: Problems with record visibility and how it is computedXuekun Hu4 Feb
          • Re: Problems with record visibility and how it is computedAnn W. Harrison28 Jan
  • Quick question on row countsKeith Murphy24 Jan
    • Re: Quick question on row countsJim Starkey25 Jan
      • Re: Quick question on row countsKeith Murphy25 Jan