[GitHub] [arrow-adbc] lidavidm commented on a diff in pull request #723: feat(c/driver/postgresql): Implement GetObjects for columns

["lidavidm (via GitHub)" <gi...@apache.org>]

lidavidm commented on code in PR #723:
URL: https://github.com/apache/arrow-adbc/pull/723#discussion_r1214356637


##########
c/driver/postgresql/connection.cc:
##########
@@ -354,22 +369,174 @@ class PqGetObjectsHelper {
       const char* table_name = row[0].data;
       const char* table_type = row[1].data;
 
-      if (depth_ > ADBC_OBJECT_DEPTH_TABLES) {
-        return ADBC_STATUS_NOT_IMPLEMENTED;
+      CHECK_NA(INTERNAL,
+               ArrowArrayAppendString(table_name_col_, ArrowCharView(table_name)),
+               error_);
+      CHECK_NA(INTERNAL,
+               ArrowArrayAppendString(table_type_col_, ArrowCharView(table_type)),
+               error_);
+      if (depth_ == ADBC_OBJECT_DEPTH_TABLES) {
+        CHECK_NA(INTERNAL, ArrowArrayAppendNull(table_columns_col_, 1), error_);
+        CHECK_NA(INTERNAL, ArrowArrayAppendNull(table_constraints_col_, 1), error_);
       } else {
+        auto table_name_s = std::string(table_name);
+        RAISE_ADBC(AppendColumns(schema_name, table_name_s));
+        RAISE_ADBC(AppendConstraints(schema_name, table_name_s));
+      }
+      CHECK_NA(INTERNAL, ArrowArrayFinishElement(schema_table_items_), error_);
+    }
+
+    CHECK_NA(INTERNAL, ArrowArrayFinishElement(db_schema_tables_col_), error_);
+    return ADBC_STATUS_OK;
+  }
+
+  AdbcStatusCode AppendColumns(std::string schema_name, std::string table_name) {
+    struct StringBuilder query = {0};
+    if (StringBuilderInit(&query, /*initial_size*/ 512)) {
+      return ADBC_STATUS_INTERNAL;
+    }
+
+    std::vector<std::string> params = {schema_name, table_name};
+    const char* stmt =
+        "SELECT attr.attname, attr.attnum, "
+        "pg_catalog.col_description(cls.oid, attr.attnum) "
+        "FROM pg_catalog.pg_attribute AS attr "
+        "INNER JOIN pg_catalog.pg_class AS cls ON attr.attrelid = cls.oid "
+        "INNER JOIN pg_catalog.pg_namespace AS nsp ON nsp.oid = cls.relnamespace "
+        "WHERE attr.attnum > 0 AND NOT attr.attisdropped "
+        "AND nsp.nspname LIKE $1 AND cls.relname LIKE $2";
+
+    if (StringBuilderAppend(&query, "%s", stmt)) {
+      StringBuilderReset(&query);
+      return ADBC_STATUS_INTERNAL;
+    }
+
+    if (column_name_ != NULL) {
+      if (StringBuilderAppend(&query, "%s", " AND attr.attname LIKE $3")) {
+        StringBuilderReset(&query);
+        return ADBC_STATUS_INTERNAL;
+      }
+
+      params.push_back(std::string(column_name_));
+    }
+
+    auto result_helper = PqResultHelper{conn_, query.buffer, params, error_};
+    StringBuilderReset(&query);
+
+    RAISE_ADBC(result_helper.Prepare());
+    RAISE_ADBC(result_helper.Execute());
+
+    for (PqResultRow row : result_helper) {
+      const char* column_name = row[0].data;
+      const char* position = row[1].data;
+
+      CHECK_NA(INTERNAL,
+               ArrowArrayAppendString(column_name_col_, ArrowCharView(column_name)),
+               error_);
+      int ival = atol(position);
+      CHECK_NA(INTERNAL,
+               ArrowArrayAppendInt(column_position_col_, static_cast<int64_t>(ival)),
+               error_);
+      if (row[2].is_null) {
+        CHECK_NA(INTERNAL, ArrowArrayAppendNull(column_remarks_col_, 1), error_);
+      } else {
+        const char* remarks = row[2].data;
         CHECK_NA(INTERNAL,
-                 ArrowArrayAppendString(table_name_col_, ArrowCharView(table_name)),
+                 ArrowArrayAppendString(column_remarks_col_, ArrowCharView(remarks)),
+                 error_);
+      }
+
+      // no xdbc_ values for now

Review Comment:
   Basically, JDBC and ODBC provide a lot of per-column metadata that is roughly consistent with each other. Flight SQL also wants to supply this metadata, rather than define it twice, it was unified into a single set of 'xDBC' metadata.



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