In Release 5.2, the polygon cache for rendering was deprecated and will be completely removed in a subsequent release. Any poly cache rendering in your code must be reworked to use dynamic poly rending. This topic describes how to migrate poly cache code to dynamic, cacheless rendering.
Caching poly buffers has two main drawbacks, both of which have a significant impact on memory:
The cache cannot span multiple GPUs.
The entire table is cached, regardless of the filter in the query.
In contrast, dynamic poly rendering can utilize all available GPUs and only uses the data that passes any filters.
To move to dynamic poly rendering, determine if you are using the poly cache, and then adjust your code if needed.
HEAVY.AI strongly recommends that you also remove the render-poly-cache-bytes
option from your server configuration file, if used. This will help prevent startup warnings or errors in subsequent releases of HEAVY.AI.
It may not be immediately obvious if you are using poly cache rendering because no flag is used to enable it. Instead, poly cache rendering is enabled according to the SQL code used in a poly-formatted data block of Vega code. If the query ultimately projects or results in a POLYGON/MULTIPOLYGON column, the cache is not used and no code changes are requried.
However, if the query does not reference a POLYGON/MULTIPOLYGON column, but projects a rowid
column, then poly caching is in use.
The following Vega code has a poly query that uses the cache system:
The sql
property of the polys
data block, which uses "format": "polys"
, projects a rowid
column. This activates poly caching, even though the geo column (heavyai_geo
in this case) is used in the filter.
To convert this Vega code to dynamic, cacheless rendering, change the SQL query:
You can keep rowid
in this query and use it for later hit-testing. It's presence does not affect dynamic rendering. See the simple projection query in Example 1 for an example.
Alternatively, you can check the INFO logs to see if poly caching is used. Look for a LOG statement similar to the following:
or
If you find either of these, then a poly cache render query is used.
To migrate from poly cache to dynamic poly rendering, you output a POLYGON/MULTIPOLYGON column in the SQL query of a poly-formatted data
block of your Vega code. In the following examples, the heavyai_geo column is a MULTIPOLYGON.
Cached (only rowid
is output):
Dynamic (heavyai_geo is now projected, along with rowid
):
Example 2 - Join query using a WITH subquery
Cached (no geo column is projected in the outer query of the join):
Dynamic (the geo column is projected in place of rowid
):