Teradata Parallel Data Pump

Chapter 3: Teradata TPump Commands
DML
The Atomic Upsert Feature
The basic upsert function has been enhanced to support an Atomic upsert capability. This
enhancement permits Teradata TPump to perform single-row upserts in a single pass. This
one-pass logic adopts the upsert-handling technique used by MultiLoad. The one-pass logic is
designated Atomic to distinguish the grouping of paired UPDATE and INSERT statements
which are executed as a single SQL statement.
The syntax for Atomic upsert consists of an UPDATE statement and an INSERT statement,
separated by an ELSE keyword.
Existing Teradata TPump scripts using the Atomic upsert form do not have to be changed.
Teradata TPump will automatically convert the old UPDATE/INSERT pairs to the Atomic
upsert feature whenever appropriate. Any attempts to change this will result in a syntax error.
The new syntax, which can also be used by CLIv2 and BTEQ applications, is dependent on
whether or not the database version, against which the Teradata TPump job is run, supports
this feature. If the database does not support Atomic Upsert, Teradata TPump reverts to the
earlier logic of sending the INSERT request if an UPDATE request fails.
The three basic constraints on the upsert feature are:
• SAME TABLE: The UPDATE and INSERT statements must specify the same table.
• SAME ROW: The UPDATE and INSERT statements must specify the same row; that is, the
primary index value in the INSERT row must be the same as the primary value in the
targeted UPDATE row.
• HASHED ROW ACCESS: The UPDATE fully specifies the primary index, allowing the
target row to be accessed with a one-AMP hashed operation.
Although Teradata TPump does not verify basic upsert constraints, Teradata Database will
reject Atomic upsert constructs that fail the constraint test, and notify Teradata TPump by
returning an appropriate error message to the client.
If the Atomic Upsert is done on a Temporal table, the optional Temporal qualifier can only be
added before the UPDATE statement.
Other Restrictions on Atomic Upsert Feature
Some of these restrictions concern syntax that is supported in UPDATE and INSERT
statements separately, but not when combined in an Atomic upsert statement. Other
restrictions concern the upsert feature's not supporting certain Teradata Database features
such as triggers and join/hash indexes, meaning that the upsert statement cannot be used on
any table utilizing those features.
The following restrictions are not supported by the Atomic upsert feature, and return an error
if submitted to Teradata Database:
• INSERT … SELECT: Syntax not supported. The INSERT may not use a subquery to
specify any of the inserted values. Note that support of this syntax is likely to be linked to
support of subqueries in the UPDATE's WHERE clause constraints as described above,
and may involve new syntax features to allow the UPDATE and INSERT to effectively
reference the same subquery.
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