Microsoft SQL Server 2008 R2 Specifications download pdf (Page 141)

Data Management CHAPTER 6 121

Query Processing

Query processing in Parallel Data Warehouse is more complex than in an SMP data ware-

house because processing must manage high availability, parallelization, and data movement

between nodes. In general, Parallel Data Warehouse’s control node follows these steps to

process a query (shown in Figure 6-5):

1. Parse the SQL statement.

2. Validate and authorize the objects.

3. Build a distributed execution plan.

4. Run the execution plan.

5. Aggregate query results.

6. Send results to the client application.

Client

Management

Compute

Control

Compute

Landing Zone

Compute

Backup

Compute

Appliance

Create query plan

User query

Query results

Aggregate query results Compute nodes

process query plan

operations in parallel

FIGURE 6-5 Query processing steps

A query with a simple join on columns of replicated tables or distribution columns of dis-

tributed tables does not require the transfer of data between compute nodes before execut-

ing the query. By contrast, a more complex join that includes a nondistribution column of a

distributed table does require Parallel Data Warehouse to copy data among the distributions

before executing the query.

Data Load Processing

The design of data load processing in Parallel Data Warehouse takes full advantage of the

parallel architecture to move data to the compute nodes. You have several options for load-

ing data into your data warehouse. You can use your ETL process to copy les to the Parallel

1 2 ... 136 137 138 139 140 141 142 143 144 145 146 ... 235 236

No comments

Microsoft SQL Server 2008 R2 Specifications Page 141