Add Metrics Support in the CAPI

[maiadegraaf]

This PR adds six new functions to the CAPI to support recursive access to the profiling tree.

• duckdb_profiling_info duckdb_get_profiling_info(duckdb_connection connection);
  • Returns the root node from the profiling information. Returns NULL if profiling is not enabled
• const char *duckdb_profiling_info_get_value(duckdb_profiling_info info, const char *key);
  • Returns the value of the setting key of the current profiling info node. If the setting does not exist or is not enabled, nullptr is returned. The result must be freed with duckdb_free.
• idx_t duckdb_profiling_info_get_child_count(duckdb_profiling_info info);
  • Returns the number of children of the current profiling info node.
• duckdb_profiling_info duckdb_profiling_info_get_child(duckdb_profiling_info info, idx_t index);
  • Returns the child node at the specified index.
• const char *duckdb_profiling_info_get_name(duckdb_profiling_info info);
  • Returns the name of the current profiling info node, if the node is an operator node. Returns nullptr otherwise. The result must be freed with duckdb_free.
• const char *duckdb_profiling_info_get_query(duckdb_profiling_info info);
  • Returns the query of the current profiling info node, if the node is the query root node. Returns nullptr otherwise. The result must be freed with duckdb_free.

Node Structure

The top node contains the QUERY_ROOT, which holds the query, the overall metrics for the query, as well as its children. Every subsequent node is an OPERATOR node which holds the operator name, the operator-specific metrics, and its children.

See this file for an example on how to access the profiling tree using the above functions.

Note: The current CAPI profiling does not include detailed profiling.

[taniabogatsch]

Hey! Thanks for the PR, this looks great! My comments are mostly structural and nits, I think functionality-wise this is good to go. :)

[taniabogatsch]

Hey @maiadegraaf - this looks almost ready to go now from my side, I only had two minor comments.

[Mytherin]

Looks good from my side - one minor comment

[Mytherin]

Thanks!