MARK_DESIGN_KSAFE

Use MARK_DESIGN_KSAFE to enable or disable automatic recovery in case of a failure. Before enabling automatic recovery, MARK_DESIGN_KSAFE queries the catalog to determine whether or not a cluster's physical schema design meets the following requirements:

• Dimension tables are replicated on all nodes.
• Fact table superprojections are segmented with each segment on a different node.
• Each fact table projection has at least one "buddy" projection.
• Each segment of each fact table projection exists on two nodes.

  Two projections are considered to be buddies if they contain the same columns and have the same segmentation. They can have different sort orders.

  MARK_DESIGN_KSAFE does not change the physical schema in any way.

Syntax

SELECT MARK_DESIGN_KSAFE(k)

Semantics

If you specify a k value of one (1), Vertica returns one of the following messages:

Marked design 1-safe

or

The schema does not meet requirements for K=1.

Fact table projection projection-name

has insufficient "buddy" projections..

The database's internal automatic recovery state persists across database restarts but is not checked at startup time.

To illustrate, consider the following sequence of events:

1. Your database has automatic recovery enabled.
2. You drop a table (and corresponding projections) in a running database.
3. You forget to MARK_DESIGN_KSAFE(0).
4. You shut down the database.
5. You start the database with automatic recovery enabled.
6. Recovery fails because the physical schema design no longer meets requirements.

Notes

• In a newly-created database, automatic recovery is disabled by default.
• If a database has had automatic recovery enabled, you must temporarily disable automatic recovery in order to create a new table.
• For information about monitoring K-Safety, see VT_SYSTEM in the SQL Virtual Tables (Monitoring API).

Examples

> SELECT MARK_DESIGN_KSAFE(1);

mark_design_ksafe

----------------------

Marked design 1-safe

(1 row)

If the physical schema design is not K-safe, messages indicate which projections do not have a buddy:

> SELECT MARK_DESIGN_KSAFE(1);

The given K value is not correct; the schema is 0-safe

Projection pp1 has 0 buddies, which is smaller that the given K of 1

Projection pp2 has 0 buddies, which is smaller that the given K of 1

(1 row)