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Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

STV_BLOCKLIST

STV_BLOCKLIST contains the number of 1 MB disk blocks that are used by each slice, table, or column in a database.

Use aggregate queries with STV_BLOCKLIST, as the following examples show, to determine the number of 1 MB disk blocks allocated per database, table, slice, or column. You can also use STV_PARTITIONS to view summary information about disk utilization.

STV_BLOCKLIST is visible only to superusers. For more information, see Visibility of Data in System Tables and Views.

Table Columns

Column Name Data Type Description
slice integer Node slice.
col integer Zero-based index for the column. Every table you create has three hidden columns appended to it: INSERT_XID, DELETE_XID, and ROW_ID (OID). A table with 3 user-defined columns contains 6 actual columns, and the user-defined columns are internally numbered as 0, 1, and 2. The INSERT_XID, DELETE_XID, and ROW_ID columns are numbered 3, 4, and 5, respectively, in this example.
tbl integer Table ID for the database table.
blocknum integer ID for the data block.
num_values integer Number of values contained on the block.
extended_limits integer For internal use.
minvalue bigint Minimum data value of the block. Stores first eight characters as 64-bit integer for non-numeric data. Used for disk scanning.
maxvalue bigint Maximum data value of the block. Stores first eight characters as 64-bit integer for non-numeric data. Used for disk scanning.
sb_pos integer Internal Amazon Redshift identifier for super block position on the disk.
pinned integer Whether or not the block is pinned into memory as part of pre-load. 0 = false; 1 = true. Default is false.
on_disk integer Whether or not the block is automatically stored on disk. 0 = false; 1 = true. Default is false.
modified integer Whether or not the block has been modified. 0 = false; 1 = true. Default is false.
hdr_modified integer Whether or not the block header has been modified. 0 = false; 1 = true. Default is false.
unsorted integer Whether or not a block is unsorted. 0 = false; 1 = true. Default is true.
tombstone integer For internal use.
preferred_diskno integer Disk number that the block should be on, unless the disk has failed. Once the disk has been fixed, the block will move back to this disk.
temporary integer Whether or not the block contains temporary data, such as from a temporary table or intermediate query results. 0 = false; 1 = true. Default is false.
newblock integer Indicates whether or not a block is new (true) or was never committed to disk (false). 0 = false; 1 = true.
num_readers integer Number of references on each block.
flags integer Internal Amazon Redshift flags for the block header.

Sample Queries

STV_BLOCKLIST contains one row per allocated disk block, so a query that selects all the rows potentially returns a very large number of rows. We recommend using only aggregate queries with STV_BLOCKLIST.

The SVV_DISKUSAGE view provides similar information in a more user-friendly format; however, the following example demonstrates one use of the STV_BLOCKLIST table.

To determine the number of 1 MB blocks used by each column in the VENUE table, type the following query:

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select col, count(*) from stv_blocklist, stv_tbl_perm where stv_blocklist.tbl = stv_tbl_perm.id and stv_blocklist.slice = stv_tbl_perm.slice and stv_tbl_perm.name = 'venue' group by col order by col;

This query returns the number of 1 MB blocks allocated to each column in the VENUE table, shown by the following sample data:

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col | count -----+------- 0 | 4 1 | 4 2 | 4 3 | 4 4 | 4 5 | 4 7 | 4 8 | 4 (8 rows)

The following query shows whether or not table data is actually distributed over all slices:

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select trim(name) as table, stv_blocklist.slice, stv_tbl_perm.rows from stv_blocklist,stv_tbl_perm where stv_blocklist.tbl=stv_tbl_perm.id and stv_tbl_perm.slice=stv_blocklist.slice and stv_blocklist.id > 10000 and name not like '%#m%' and name not like 'systable%' group by name, stv_blocklist.slice, stv_tbl_perm.rows order by 3 desc;

This query produces the following sample output, showing the even data distribution for the table with the most rows:

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table | slice | rows ----------+-------+------- listing | 13 | 10527 listing | 14 | 10526 listing | 8 | 10526 listing | 9 | 10526 listing | 7 | 10525 listing | 4 | 10525 listing | 17 | 10525 listing | 11 | 10525 listing | 5 | 10525 listing | 18 | 10525 listing | 12 | 10525 listing | 3 | 10525 listing | 10 | 10525 listing | 2 | 10524 listing | 15 | 10524 listing | 16 | 10524 listing | 6 | 10524 listing | 19 | 10524 listing | 1 | 10523 listing | 0 | 10521 ... (180 rows)

The following query determines whether any tombstoned blocks were committed to disk:

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select slice, col, tbl, blocknum, newblock from stv_blocklist where tombstone > 0; slice | col | tbl | blocknum | newblock -------+-----+--------+----------+---------- 4 | 0 | 101285 | 0 | 1 4 | 2 | 101285 | 0 | 1 4 | 4 | 101285 | 1 | 1 5 | 2 | 101285 | 0 | 1 5 | 0 | 101285 | 0 | 1 5 | 1 | 101285 | 0 | 1 5 | 4 | 101285 | 1 | 1 ... (24 rows)