lidavidm commented on code in PR #4694:
URL: https://github.com/apache/arrow-adbc/pull/4694#discussion_r3899136323
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c/include/arrow-adbc/adbc.h:
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@@ -1087,6 +1093,582 @@ const struct AdbcError* AdbcErrorFromArrayStream(struct
ArrowArrayStream* stream
/// @}
+/// \defgroup adbc-statement-metadata-collection Metadata Collections
+///
+/// Fetch (catalog) metadata from the database. On a statement, set
+/// ADBC_METADATA_COLLECTION to one of the collection names below, and set any
+/// filters via the options defined below. (There are driver/vendor-specific
+/// collections and filters as well.) Then call AdbcStatementExecuteQuery or
+/// AdbcStatementExecuteSchema. The result is an Arrow dataset with a schema
+/// defined by the collection. For example, a client may request a list of
+/// tables in the database, or a list of supported data types.
+///
+/// All drivers must implement a collection called "meta" (which is aliased to
+/// NULL and blank string) that defines the available collections. See
+/// ADBC_METADATA_COLLECTION_META.
+///
+/// Drivers may also implement AdbcStatementRequestSchema to (1) request
+/// different data types and (2) drop fields from the result. Drivers are not
+/// required to support this, and are not required to support other changes
+/// like reordering collection fields. Drivers are encouraged to use this to
+/// give applications flexibility over output type and shape (e.g. reducing
+/// memory pressure by run-end-encoding or dictionary-encoding primary key
+/// columns; optimizing queries by using simpler queries and eliminating joins
+/// if the application drops certain columns). Unless requested, however,
+/// drivers should return the type specified below and not substitute a
+/// logically equivalent type (e.g. utf8 below should be a string array by
+/// default, and not a utf8view or large string or other array).
+///
+/// Drivers may add more fields at the end of standard schemas to reflect
+/// vendor-specific metadata. Applications must access these by name or using
+/// an offset from the end of the schema and cannot assume that the index of
+/// the field will remain stable. Hence, it is discouraged to access these
+/// fields by ordinal as this is brittle. Drivers must add the fields at the
+/// end and must prefix field names with the vendor/driver name to
+/// differentiate them (e.g. 'POSTGRESQL:owner', not just 'owner').
+///
+/// Similarly, future standard revisions may add more fields to existing
+/// standard schemas. Applications must not assume the number of fields is
+/// fixed.
+///
+/// Drivers may implement collections beyond those defined by ADBC, but must
+/// use a vendor-specific prefix (e.g. `postgresql.`) to avoid conflicts with
+/// future standardized collections. Drivers must not use the `adbc.` prefix.
+///
+/// Drivers may not necessarily accept filter options or other options before
+/// the collection name option is set.
+///
+/// This is intended to replace AdbcConnectionGetObjects, but both APIs will
+/// be supported for the time being. AdbcConnectionGetObjects may be
+/// deprecated in a future revision.
+///
+/// \since ADBC API revision 1.2.0
+///
+/// @{
+
+/// \brief Prepare to fetch a metadata collection.
+///
+/// The type is char*.
+#define ADBC_METADATA_COLLECTION "adbc.metadata.collection"
+
+/// \brief Filter the collection on the literal catalog name.
+///
+/// The type is char*.
+#define ADBC_METADATA_FILTER_CATALOG "adbc.metadata.filter.catalog"
+
+/// \brief Filter the collection on the catalog name, matching a search
+/// pattern.
Review Comment:
"search pattern" is already broadly defined in this header
https://github.com/apache/arrow-adbc/blob/be5f50f0887b820b901f6fb979e608c6488caf11/c/include/arrow-adbc/adbc.h#L1510-L1515
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