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by fulafel 1317 days ago
PG ships with Lua support: https://www.postgresql.org/docs/current/external-pl.html

(Also Python, Javascript, and Java)

I don't know specifics about the API coverage. It seems this extension mostly just implements new SQL visible functions and data types, which should be doable from those languages as well. Composite types might have to be defined as PG records (or json) instead of C level new PG object types.
1 comments
nine_k 1317 days ago
You can write stored procedures in it. Which is fine.

You cannot though write a new storage engine, a new kind of index, or something else that takes an extension.

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fulafel 1316 days ago
I think very few PG extension use cases need new storage engines. Looking at https://age.incubator.apache.org/overview/ it says it's using the normal PG storage.

Regarding indexes - (1) you can implement most custom indexe scenarios based on supplied expressions involving custom functions: https://www.postgresql.org/docs/current/indexes-expressional... (2) I suspect for the graph use case you could leverage json indexes: https://www.postgresql.org/docs/current/datatype-json.html#J...

This is not to claim with any high degree of certainty that this could be implemented in PG/Lua, just from my armchair there doesn't seem anything immediately obvious that would prevent it.

For example the querying in AGE is syntactically implemented in the function cypher() that is used in the examples to receiving custom syntax as strings with the "dollar quoting"[1] syntax:

  SELECT *
   FROM cypher('graph_name', $$
     MATCH (n)
     WHERE exists(n.surname)
     RETURN n.first_name, n.last_name $$) as (first_name agtype, last_name agtype);
[1] https://www.postgresql.org/docs/current/sql-syntax-lexical.h...
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