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

SVV_DISKUSAGE

Amazon Redshift creates the SVV_DISKUSAGE system view by joining the STV_TBL_PERM and STV_BLOCKLIST tables. The SVV_DISKUSAGE view contains information about data allocation for the tables in a database.

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

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

Table Columns

Column Name Data Type Description
db_id integer Database ID.
name character(72) Table name.
slice integer Data slice allocated to the table.
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.
blocknum integer ID for the data block.
num_values integer Number of values contained on the block.
minvalue bigint Minimum value contained on the block.
maxvalue bigint Maximum value contained on the block.
sb_pos integer Internal identifier for the position of the super block on 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.

Sample Queries

SVV_DISKUSAGE 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 SVV_DISKUSAGE.

Return the highest number of blocks ever allocated to column 6 in the USERS table (the EMAIL column):

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select db_id, trim(name) as tablename, max(blocknum) from svv_diskusage where name='users' and col=6 group by db_id, name; db_id | tablename | max --------+-----------+----- 175857 | users | 2 (1 row)

The following query returns similar results for all of the columns in a large 10-column table called SALESNEW. (The last three rows, for columns 10 through 12, are for the hidden metadata columns.)

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select db_id, trim(name) as tablename, col, tbl, max(blocknum) from svv_diskusage where name='salesnew' group by db_id, name, col, tbl order by db_id, name, col, tbl; db_id | tablename | col | tbl | max --------+------------+-----+--------+----- 175857 | salesnew | 0 | 187605 | 154 175857 | salesnew | 1 | 187605 | 154 175857 | salesnew | 2 | 187605 | 154 175857 | salesnew | 3 | 187605 | 154 175857 | salesnew | 4 | 187605 | 154 175857 | salesnew | 5 | 187605 | 79 175857 | salesnew | 6 | 187605 | 79 175857 | salesnew | 7 | 187605 | 302 175857 | salesnew | 8 | 187605 | 302 175857 | salesnew | 9 | 187605 | 302 175857 | salesnew | 10 | 187605 | 3 175857 | salesnew | 11 | 187605 | 2 175857 | salesnew | 12 | 187605 | 296 (13 rows)