Querying Data v6.27.4

This topic provides information about using SQL in WarehousePGs.

You enter SQL statements called queries to view, change, and analyze data in a database using the psql interactive SQL client and other client tools.

• About WarehousePG Query Processing
  This topic provides an overview of how WarehousePG processes queries. Understanding this process can be useful when writing and tuning queries.
• About GPORCA
  In WarehousePG, the default GPORCA optimizer co-exists with the Postgres Planner.
• Defining Queries
  WarehousePG is based on the PostgreSQL implementation of the SQL standard.
• WITH Queries (Common Table Expressions)
  The WITH clause provides a way to use subqueries or perform a data modifying operation in a larger SELECT query. You can also use the WITH clause in an INSERT, UPDATE, or DELETE command.
• Using Functions and Operators
  Description of user-defined and built-in functions and operators in WarehousePG.
• Working with JSON Data
  WarehousePG supports the json and jsonb data types that store JSON (JavaScript Object Notation) data.
• Working with XML Data
  WarehousePG supports the xml data type that stores XML data.
• Using Full Text Search
  WarehousePG provides data types, functions, operators, index types, and configurations for querying natural language documents.
• Using WarehousePG MapReduce
  MapReduce is a programming model developed by Google for processing and generating large data sets on an array of commodity servers. WarehousePG MapReduce allows programmers who are familiar with the MapReduce model to write map and reduce functions and submit them to the WarehousePG parallel engine for processing.
• Query Performance
  WarehousePG dynamically eliminates irrelevant partitions in a table and optimally allocates memory for different operators in a query.
• Managing Spill Files Generated by Queries
  WarehousePG creates spill files, also known as workfiles, on disk if it does not have sufficient memory to run an SQL query in memory.
• Query Profiling
  Examine the query plans of poorly performing queries to identify possible performance tuning opportunities.

Parent topic: WarehousePG Administrator Guide