catalog: surface view column comments via duckdb_columns()

ViewInfo gains a column_comments map decoded in ParseViewInfo and fed
into CreateViewInfo.column_comments_map so DuckDB exposes per-column
comments on VGI views, the way table column comments already work.

VgiSchemaEntry::Scan(TABLE_ENTRY) now also scans the views set: DuckDB
stores tables and views in a single CatalogSet, so duckdb_columns()
(which scans TABLE_ENTRY) expects views there too. Without this, VGI
views never appeared in duckdb_columns() at all.

comments.test covers view column comments and view tags.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: rustyconover

src/generated/vgi_protocol_schemas.hpp

@@ -2,7 +2,7 @@
 // GENERATED by vgi.codegen.cpp_schemas. DO NOT EDIT BY HAND.
 //
 // Generator: vgi-gen-cpp-schemas v1
-// Content hash: e54a1f0bf14e
+// Content hash: 06a70f707a52
 //
 // To regenerate:
 //   uv run --project ~/Development/vgi-python vgi-gen-cpp-schemas \
@@ -81,6 +81,7 @@ inline const std::shared_ptr<arrow::Schema> &ViewInfoSchema() {
 	    arrow::field("name", arrow::utf8(), /*nullable=*/false),
 	    arrow::field("schema_name", arrow::utf8(), /*nullable=*/false),
 	    arrow::field("definition", arrow::utf8(), /*nullable=*/false),
+	    arrow::field("column_comments", arrow::map(arrow::utf8(), arrow::utf8()), /*nullable=*/false),
 	});
 	return schema;
 }

src/include/vgi_catalog_api.hpp

@@ -467,6 +467,9 @@ struct VgiViewInfo {
 	std::string definition; // SQL query defining the view
 	std::string comment;
 	std::map<std::string, std::string> tags;
+	// Per-column comments keyed by the view's output column name. Fed into
+	// CreateViewInfo.column_comments_map so they surface via duckdb_columns().
+	std::map<std::string, std::string> column_comments;
 };
 
 // Macro metadata from the worker

src/storage/vgi_schema_entry.cpp

@@ -395,7 +395,14 @@ void VgiSchemaEntry::Scan(ClientContext &context, CatalogType type,
                           const std::function<void(CatalogEntry &)> &callback) {
 	switch (type) {
 	case CatalogType::TABLE_ENTRY:
+		// DuckDB stores tables and views in a single CatalogSet, so a TABLE_ENTRY
+		// scan naturally surfaces both — duckdb_tables()/duckdb_constraints() then
+		// skip non-table entries by type, while duckdb_columns() dispatches views
+		// to its ViewColumnHelper (which binds the view to expose its columns and
+		// column comments). VGI keeps views in a separate set, so we must include
+		// them here too; otherwise VGI views never appear in duckdb_columns().
 		tables_.Scan(context, callback);
+		views_.Scan(context, callback);
 		break;
 	case CatalogType::VIEW_ENTRY:
 		views_.Scan(context, callback);

src/storage/vgi_view_set.cpp

@@ -31,6 +31,11 @@ static unique_ptr<ViewCatalogEntry> CreateViewEntryFromInfo(Catalog &catalog, Sc
 	for (auto &[key, val] : view_info.tags) {
 		info.tags[key] = val;
 	}
+	// Per-column comments — DuckDB aligns these by name against the columns it
+	// binds from the view's SQL and exposes them via duckdb_columns().
+	for (auto &[col, comment] : view_info.column_comments) {
+		info.column_comments_map[col] = Value(comment);
+	}
 	// Parse SQL to get SelectStatement
 	try {
 		Parser parser;

src/vgi_catalog_api.cpp

@@ -1952,6 +1952,7 @@ VgiViewInfo ParseViewInfo(const std::shared_ptr<arrow::RecordBatch> &batch, cons
 	info.definition = row["definition"].value_not_null<std::string>();
 	info.comment = row["comment"].value_or("");
 	info.tags = row["tags"].value_not_null<std::map<std::string, std::string>>();
+	info.column_comments = row["column_comments"].value_not_null<std::map<std::string, std::string>>();
 
 	return info;
 }

test/sql/integration/table/comments.test

@@ -64,6 +64,56 @@ ORDER BY view_name;
 even_numbers	Even numbers from 0 to 98
 first_ten	First 10 integers
 
+# ============================================================================
+# View tags (via duckdb_views)
+# ============================================================================
+
+# first_ten declares view-level tags; even_numbers declares none (empty map).
+query TT
+SELECT view_name, tags
+FROM duckdb_views()
+WHERE database_name = 'example' AND schema_name = 'main'
+ORDER BY view_name;
+----
+even_numbers	{}
+first_ten	{layer=demo, origin=sequence}
+
+# ============================================================================
+# View column comments (via duckdb_columns)
+# ============================================================================
+
+# first_ten (main schema) carries a comment on its single output column `n`.
+query TT
+SELECT column_name, comment
+FROM duckdb_columns()
+WHERE database_name = 'example' AND schema_name = 'main'
+  AND table_name = 'first_ten'
+ORDER BY column_name;
+----
+n	Sequence index 0..9
+
+# small_numbers (data schema) carries a comment on its `value` column —
+# exercises a view column comment outside the default schema, aligned by name.
+query TT
+SELECT column_name, comment
+FROM duckdb_columns()
+WHERE database_name = 'example' AND schema_name = 'data'
+  AND table_name = 'small_numbers'
+ORDER BY column_name;
+----
+value	Single-digit value 0..9
+
+# even_numbers has a view-level comment but no column comments, so its column
+# `n` must report a NULL comment (commented view != commented columns).
+query TT
+SELECT column_name, comment
+FROM duckdb_columns()
+WHERE database_name = 'example' AND schema_name = 'main'
+  AND table_name = 'even_numbers'
+ORDER BY column_name;
+----
+n	NULL
+
 # ============================================================================
 # Column comments on products table (via duckdb_columns)
 # ============================================================================