Hi, Mateusz.
1. Is it possible to implement MariaDB extensions like Spatial (custom
type + set of functions) without such a tight coupling with the
internal implementation of the type system (without messing Field
class with geometry types directly, etc.)?
Yes, it is possible. The core algorithms are separated from the Field
structure and any other database internals.
They are placed in sql/gcalc_slicescan.cc and sql/gcalc_tools.cc files.
2. Is it possible to implement Spatial using User-Defined Functions
(UDF) defined in shared binary?
The spatial functions/operations can be implemented with UDF, but
that makes query optimization and using Spatial keys problemmatic.
3. What is the reason behind using Well-Known-Binary (WKB) stream of
bytes to transport geometry values into/from functions? Is it due to
limitations of MariaDB type system where String is the only universal
carrier for complex data? This concern is related to necessity of
encoding/decoding WKB when chaining spatial function calls, and
possibilities to avoid it.
The reason was mostly historical. It was sufficient for the first
implementations of the
Geometry field types and somewhat convenient as we don't need to perform
conversions
when we need to import/export features in their WKB representation.
But yes, that format is inefficient and difficult to handle properly. I
plan to get rid of it
internally - only support importing-exporting it.
Best regards.
HF
23.09.2013 18:46, Mateusz Loskot wrote:
Hi,
I'm going to ask question about how the current Spatial Extensions are
implemented.
I have spent some time reading the source code in the current trunk
(spatial.h|cc, gcal*.h|cc, related Field and Item definitions, etc.),
so I have a rough understanding of the overall structure, how the
geometry data types are implemented and exposed to SQL, how the
spatial functions are defined and registered. I did not looked into
details of implementation of geospatial algorithms, but that's too low
level for the question I'm going to ask.
Initially, I was going to ask very detailed question, listing all the
relevant code definitions and asking separately about each of them,
but that's not necessary at this stage, I think.
Instead, I'm going to simplify and ask about the bigger picture, more
about MariaDB extensions API:
1. Is it possible to implement MariaDB extensions like Spatial (custom
type + set of functions) without such a tight coupling with the
internal implementation of the type system (without messing Field
class with geometry types directly, etc.)?
2. Is it possible to implement Spatial using User-Defined Functions
(UDF) defined in shared binary?
3. What is the reason behind using Well-Known-Binary (WKB) stream of
bytes to transport geometry values into/from functions? Is it due to
limitations of MariaDB type system where String is the only universal
carrier for complex data? This concern is related to necessity of
encoding/decoding WKB when chaining spatial function calls, and
possibilities to avoid it.
Best regards,
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