| Attachment | Size |
|---|---|
 stats_td14_20130830.zip | 212.2 KB |
Beginning with TD14 statistics are no longer stored in dbc.TVFields and dbc.Indexes, they have been moved into dbc.StatsTbl to facilitate several enhancements. A new view dbc.StatsV returns much of the information previously extracted in my StatsInfo query.
But of course this is still not enough information, at least not for me ;-)
dbc.StatsV vs. StatsInfo TD13/14
I tried to get the best of both worlds and so i wrote a new version for TD14 to extract as much additional data as possible. I had to remove a few columns (they're no longer needed or it's no longer possible to get that info) and i renamed some to match the new names in dbc.StatsV. Most of the new columns were simply not available before TD14.
Following table describes the new StatsInfo view and details the differences to the previous version and dbc.StatsV:
dbc.StatsV TD14 | New StatsInfo TD14 | StatsInfo TD13.10 | Remarks | Description |
|---|---|---|---|---|
| (Column added/removed/changed) |
|
| |
DatabaseName | DatabaseName | DatabaseName |
|
|
TableName | TableName | TableName |
|
|
ColumnName | ColumnName | ColumnName | StatsId <> 0 | List of comma-separated column names |
FieldIdList | FieldIdList | FieldId | StatsId <> 0 | List of semicolon-separated field ids |
StatsName | StatsName | StatsName | StatsId <> 0 | Alias name of the statistics (if assigned) |
| IndexName | IndexName | StatsId <> 0 | Name of the index (if assigned) |
| DateIncluded | DateIncluded | StatsId <> 0 | DATE or TIMESTAMP column included, Y/N |
| PartitionColumn | PartitionColumn | StatsId <> 0 | Column included which is used in the table's partitioning expression: Y/N |
| PartitionLevels | PartitionLevels |
| Number of levels in the table's partitioning expression, zero means not partitioned |
| ColumnPartitioningLevel |
|
| Level number for the column partitioning level, > 0 indicates columnar table |
| PartitionsDefined | PartitionsDefined |
| The number of partitions defined |
ExpressionCount | ExpressionCount | ColumnCount | StatsId <> 0 | The number of columns in the statistics |
StatsId | StatsId |
|
| StatsId = 0 → Summary Stats |
StatsType | StatsType |
|
| Statistics collected on: |
| StatsTypeOld | StatsType |
| Statistics collected on: |
| TableType | TableType |
| TempTbl → Global Temporary Table |
StatsSource | StatsSource |
|
| The method this statistic is acquired: |
ValidStats | ValidStats |
|
| TD14.10: Indicates whether the statistics are valid or not: Y/N |
DBSVersion | DBSVersion |
|
| Database version statistics collected on |
SampleSizePct | SampleSizePct | SampleSize | StatsId <> 0 | Sample size used for collect stats, NULL if not sampled |
SampleSignature | SampleSignature |
| StatsId <> 0 | Sample option encoded as a 10 character signature |
ThresholdSignature | ThresholdSignature |
| StatsId <> 0 | THRESHOLD options encoded as a 17 character signature (not used before TD14.10) |
MaxIntervals | MaxIntervals |
| StatsId <> 0 | User-specified maximum number of intervals |
StatsSkipCount | StatsSkipCount |
| StatsId <> 0 | TD14.10 only: How many times the statistis collection has been skipped based on the THRESHOLD |
MaxValueLength | MaxValueLength |
| StatsId <> 0 | User-specified maximum value length |
LastCollectTimestamp | LastCollectTimestamp | CollectTimestamp |
| Date and time when statistics were last collected |
| LastCollectDate | CollectDate |
| |
| LastCollectTime | CollectTime |
| |
RowCount | RowCount | NumRows |
| The cardinality of the table, i.e. the number of rows |
UniqueValueCount | UniqueValueCount | NumValues | StatsId <> 0 | Distinct Values. Estimated when sampled |
PNullUniqueValueCount | PNULLUniqueValueCount |
| StatsId <> 0 | Number of unique values from rows with partial NULLs (multicolumn stats) |
NullCount | NULLCount | NumNULLs | StatsId <> 0 | Number of partly NULL and all NULL rows, estimated when sampled |
AllNullCount | AllNULLCount | NumAllNULLs | StatsId <> 0 | Number of all NULL rows (multicolumn stats), estimated when sampled |
HighModeFreq | HighModeFreq | ModeFreq | StatsId <> 0 | Frequency of the most common value, estimated when sampled |
PNullHighModeFreq | PNULLHighModeFreq |
| StatsId <> 0 | Highest frequency of values having partial NULLs (for multicolumn stats), stimated when sampled |
AvgAmpRPV | AvgAmpRPV | AvgAmpRPV | StatsId <> 0 | Overall average of the average rows per value from each AMP, only for NUSIs, otherwise zero |
| MinValue | MinValue | StatsId <> 0 | Minimum data value (only for single column numeric or datetime stats) |
| ModalValue | ModalValue | StatsId <> 0 | Most common data value (only for single column numeric or datetime stats) |
| MaxValue | MaxValue | StatsId <> 0 | Maximum data value (only for single column numeric or datetime stats) |
| OneAMPSampleEst | OneAMPSampleEst | StatsId = 0 | Estimated cardinality based on a single-AMP sample |
| AllAmpSampleEst | AllAmpSampleEst | StatsId = 0 | Estimated cardinality based on an all-AMP sample |
DelRowCount | DelRowCount |
| StatsId = 0 | Deleted rows count??? used in 14.10 ??? |
PhyRowCount | PhyRowCount |
| StatsId = 0 | Seems to be the same as AllAMPSampleEst – used in 14.10 ??? |
AvgRowsPerBlock | AvgRowsPerBlock |
| StatsId = 0 | Average number of rows per datablock??? |
AvgBlockSize | AvgBlockSize |
| StatsId = 0 | Average datablock size??? |
BLCPctCompressed | BLCPctCompressed |
| StatsId = 0 | Blockcompression in percent??? used in 14.10 ??? |
BLCBlkUcpuCost | BLCBlkUcpuCost |
| StatsId = 0 | CPU cost for Blockcompression??? used in 14.10 ??? |
BLCBlkURatio | BLCBlkURatio |
| StatsId = 0 | ??? used in 14.10 ??? |
AvgRowSize | AvgRowSize |
| StatsId = 0 | Average record size??? |
Temperature | Temperature |
| StatsId = 0 | populated in 14.10??? |
NumOfAMPs | NumOfAMPs | NumAMPs |
| The number of AMPs from which statistics were collected, usually the number of AMPs in the system, 1 for an empty table |
CreateTimeStamp | CreateTimeStamp |
|
| Statistics creation timestamp |
LastAlterTimeStamp | LastAlterTimeStamp | LastAlterTimeStamp |
| Different meaning: Last user updated timestamp, i.e. Collect stats was submitted but skipped by optimizer due to threshold not reached |
| LastAccessTimestamp | LastAccessTimestamp |
| The last time this column/index was used in queries, the same info is found in dbc.TablesV and dbc.IndicesV |
| AccessCount | AccessCount |
| How often this column/index was used in queries, the same info is found in dbc.TablesV and dbc.IndicesV |
| TableId | TableId |
| To facilitate additional joins to other system tables |
| IndexNumber | IndexNumber | StatsId <> 0 | Index number of the index on which statistics are collected |
| FieldType | FieldType |
| Single column stats: dbc.TVFields.FieldType, NULL for multi-column |
| Version | StatsVersion |
| Internal version of statistics: |
OriginalVersion | OriginalVersion |
| StatsId <> 0 | Probably version when stats were migrated from older releases, but not yet recollected |
NumOfBiasedValues | NumOfBiasedValues |
| StatsId <> 0 | Number of biased values in the histogram |
NumOfEHIntervals | NumOfEHIntervals |
| StatsId <> 0 | Number of equal height intervals in the histogram |
NumOfRecords | NumOfRecords |
|
| Number of history records in the histogram |
| CollectStatement | CollectStatement |
| COLLECT STATS statement to collect the stats. |
| ShowStatement | HelpStatement |
| SHOW STATS VALUES statement to get the stats details. |
|
| MissingStats |
| Was a side-product of the old query, too much overhead to add |
|
| NumIntervals |
| Replaced by NumOfBiasedValues & NumOfEHIntervals |
|
| CollectDuration |
| Not (yet) possible, i don't know if this is stored somewhere |
|
| NumericStats |
| No longer neccessary |
|
| DataSize |
| Too much overhead to calculate, not really needed as the limitation of 16 bytes is removed in TD14 |
Please report any issues or obviously wrong output to dnoeth@gmx.de.
Attached files:
StatsInfo_vs_StatsV.pdf | Describes the new StatsInfo view and details the differences to the previous version and dbc.StatsV - added, modified and removed columns (same as above table) |
Teradata Statistics TD14.pdf | Partial description of the new internal stats format based on some reverse engeneering of the binary data stored in a BLOB in dbc.StatsTbl.Histogram. Luckily the internal storage maps almost 1:1 to the output of a SHOW STATISTICS VALUES :-) |
stats_td14_yyyymmdd.sql | StatsInfo source code. To keep the code clean it's based on SQL-UDFs |
ReverseBytes.sql ReverseBytes.c | Can be used to replace the ReverseBytes SQL-UDF with a C-UDF which uses way less CPU (but most DBA's don't like C). |