[PHOENIX-654] Minimize projection into scan for VIEW

• Type: Sub-task
• Status: Resolved
• Resolution: Duplicate
• Fix Version/s: 4.7.0
• old issue number: 523
• Assignee: Unassigned
• Reporter: James R. Taylor
• Created: 10/Mar/14 23:47
• Updated: 14/Jan/16 19:22
• Resolved: 14/Jan/16 19:22

Description

When you create a TABLE, we insert an empty key value into the first column family that we can count on being there for every row. For a VIEW, we don't do that, so we just fall back on projecting everything into a scan. If there are lots of columns (for example, 60,000 in [this](https://groups.google.com/forum/_!topic/phoenix-hbase-user/JgQjlqC4-uw) case), the scan is very slow.

Instead, we should only project everything when absolutely necessary, in these cases:

• IS NULL expression
• CASE WHEN with an ELSE expression
• Usages of row value constructor
• When a column in the primary key is used
• When there is no where clause
• When there is a group by of a nullable expression

We could potentially do the same for a TABLE, but the empty key value seems like a better trade off as far as performance goes. In addition, we need the empty key value as a row cannot exist without at least one key value, making it impossible to support use cases that only define a primary key.