Add PolarDB for PostgreSQL examples

cpp/postgresql/polardb-pg/CMakeLists.txt

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+# Copyright 2026 Columnar Technologies Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+cmake_minimum_required(VERSION 3.15)
+project(polardb_pg_demo CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Use conda environment paths
+if(DEFINED ENV{CONDA_PREFIX})
+    list(APPEND CMAKE_PREFIX_PATH "$ENV{CONDA_PREFIX}")
+endif()
+
+find_package(Arrow REQUIRED)
+
+add_executable(polardb_pg_demo main.cpp)
+
+if(DEFINED ENV{CONDA_PREFIX})
+    target_include_directories(polardb_pg_demo PRIVATE $ENV{CONDA_PREFIX}/include)
+    target_link_directories(polardb_pg_demo PRIVATE $ENV{CONDA_PREFIX}/lib)
+endif()
+
+target_link_libraries(polardb_pg_demo
+    adbc_driver_manager
+    Arrow::arrow_shared
+)
+
+target_compile_options(polardb_pg_demo PRIVATE
+    -Wall
+    -Werror
+)

cpp/postgresql/polardb-pg/Makefile

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+# Copyright 2026 Columnar Technologies Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+CXXFLAGS = -std=c++17 -Wall -Werror -I$(CONDA_PREFIX)/include
+LIBS = -L$(CONDA_PREFIX)/lib -ladbc_driver_manager -larrow -Wl,-rpath,$(CONDA_PREFIX)/lib
+
+polardb_pg_demo: main.cpp
+	$(CXX) $(CXXFLAGS) -o polardb_pg_demo main.cpp $(LIBS)
+
+clean:
+	rm -f polardb_pg_demo
+
+.PHONY: clean

cpp/postgresql/polardb-pg/README.md

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+<!--
+Copyright 2026 Columnar Technologies Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Connecting C++ and PolarDB for PostgreSQL with ADBC
+
+## Instructions
+
+> [!TIP]
+> If you already have a PolarDB for PostgreSQL instance running, skip the steps to set up and clean up PolarDB for PostgreSQL.
+
+### Prerequisites
+
+1. [Install dbc](https://docs.columnar.tech/dbc/getting_started/installation/)
+
+2. [Install miniforge](https://github.com/conda-forge/miniforge)
+
+3. Create and activate a new environment with the required C++ libraries:
+
+    ```sh
+    mamba create -n adbc-cpp -c conda-forge cmake compilers libadbc-driver-manager libarrow
+
+    # Initialize mamba in your shell if not already done
+    eval "$(mamba shell hook --shell zsh)"
+    mamba activate adbc-cpp
+    ```
+
+    (`cmake` is only needed if you use CMake to build the C++ program below.)
+
+### Set up PolarDB for PostgreSQL
+
+1. [Install Docker](https://docs.docker.com/get-started/get-docker/)
+
+2. Start a PolarDB for PostgreSQL instance:
+
+    ```sh
+    docker run -d --rm --name polardb \
+        --cap-add=SYS_PTRACE --privileged=true \
+        -p 5432:5432 \
+        -e POLARDB_USER=username \
+        -e POLARDB_PASSWORD=password \
+        polardb/polardb_pg_local_instance:15
+    ```
+
+### Connect to PolarDB for PostgreSQL
+
+1. Install the PostgreSQL ADBC driver:
+
+    ```sh
+    dbc install --level user postgresql
+    ```
+
+2. Customize the C++ program `main.cpp` as needed
+    - Change the connection arguments in the `AdbcDatabaseSetOption()` calls
+        - Format `uri` according to the [connection URI format used by PostgreSQL](https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING-URIS), or keep it as is
+    - If you changed which database you're connecting to, also change the SQL SELECT statement in `AdbcStatementSetSqlQuery()`
+
+3. Build and run the C++ program:
+
+    Using Make:
+    ```sh
+    make
+    ./polardb_pg_demo
+    ```
+
+    Or using CMake:
+    ```sh
+    cmake -B build
+    cmake --build build
+    ./build/polardb_pg_demo
+    ```
+
+### Clean up
+
+1. Clean build artifacts:
+
+    Using Make:
+    ```sh
+    make clean
+    ```
+
+    Using CMake:
+    ```sh
+    rm -rf build
+    ```
+
+2. Stop the Docker container running PolarDB for PostgreSQL:
+
+    ```sh
+    docker stop polardb
+    ```

cpp/postgresql/polardb-pg/main.cpp

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+// Copyright 2026 Columnar Technologies Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// For EXIT_SUCCESS
+#include <cstdlib>
+// For strerror
+#include <cstring>
+#include <iostream>
+
+#include <arrow-adbc/adbc.h>
+#include <arrow-adbc/adbc_driver_manager.h>
+#include <arrow/c/bridge.h>
+#include <arrow/record_batch.h>
+
+// Error-checking helper for ADBC calls.
+// Assumes that there is an AdbcError named `error` in scope.
+#define CHECK_ADBC(EXPR)                                                       \
+  if (AdbcStatusCode status = (EXPR); status != ADBC_STATUS_OK) {              \
+    if (error.message != nullptr) {                                            \
+      std::cerr << error.message << std::endl;                                 \
+    }                                                                          \
+    return EXIT_FAILURE;                                                       \
+  }
+
+// Error-checking helper for ArrowArrayStream.
+#define CHECK_STREAM(STREAM, EXPR)                                             \
+  if (int status = (EXPR); status != 0) {                                      \
+    std::cerr << "(" << std::strerror(status) << "): ";                        \
+    const char *message = (STREAM).get_last_error(&(STREAM));                  \
+    if (message != nullptr) {                                                  \
+      std::cerr << message << std::endl;                                       \
+    } else {                                                                   \
+      std::cerr << "(no error message)" << std::endl;                          \
+    }                                                                          \
+    return EXIT_FAILURE;                                                       \
+  }
+
+int main() {
+  AdbcError error = {};
+
+  AdbcDatabase database = {};
+  CHECK_ADBC(AdbcDatabaseNew(&database, &error));
+
+  CHECK_ADBC(AdbcDatabaseSetOption(&database, "driver", "postgresql", &error));
+  CHECK_ADBC(AdbcDatabaseSetOption(&database, "uri",
+                                   "postgresql://username:password@localhost:5432/postgres", &error));
+  CHECK_ADBC(AdbcDriverManagerDatabaseSetLoadFlags(
+      &database, ADBC_LOAD_FLAG_DEFAULT, &error));
+  CHECK_ADBC(AdbcDatabaseInit(&database, &error));
+
+  AdbcConnection connection = {};
+  CHECK_ADBC(AdbcConnectionNew(&connection, &error));
+  CHECK_ADBC(AdbcConnectionInit(&connection, &database, &error));
+
+  AdbcStatement statement = {};
+  CHECK_ADBC(AdbcStatementNew(&connection, &statement, &error));
+
+  struct ArrowArrayStream stream = {};
+  int64_t rows_affected = -1;
+
+  CHECK_ADBC(
+      AdbcStatementSetSqlQuery(&statement, "SELECT version()", &error));
+  CHECK_ADBC(
+      AdbcStatementExecuteQuery(&statement, &stream, &rows_affected, &error));
+
+  // Import stream as record batch reader
+  auto maybe_reader = arrow::ImportRecordBatchReader(&stream);
+  if (!maybe_reader.ok()) {
+    std::cerr << "Failed to import record batch reader: "
+              << maybe_reader.status().message() << std::endl;
+    return 1;
+  }
+
+  auto reader = maybe_reader.ValueOrDie();
+
+  while (true) {
+    auto maybe_batch = reader->Next();
+    if (!maybe_batch.ok()) {
+      std::cerr << "Error reading batch: " << maybe_batch.status().message()
+                << std::endl;
+      return 1;
+    }
+
+    auto batch = maybe_batch.ValueOrDie();
+    if (!batch) {
+      break;
+    }
+
+    std::cout << batch->ToString() << std::endl;
+  }
+
+  CHECK_ADBC(AdbcStatementRelease(&statement, &error));
+  CHECK_ADBC(AdbcConnectionRelease(&connection, &error));
+  CHECK_ADBC(AdbcDatabaseRelease(&database, &error));
+
+  return EXIT_SUCCESS;
+}

go/postgresql/polardb-pg/README.md

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+<!--
+Copyright 2026 Columnar Technologies Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Connecting Go and PolarDB for PostgreSQL with ADBC
+
+## Instructions
+
+> [!TIP]
+> If you already have a PolarDB for PostgreSQL instance running, skip the steps to set up and clean up PolarDB for PostgreSQL.
+
+### Prerequisites
+
+1. [Install Go](https://go.dev/doc/install)
+
+2. [Install dbc](https://docs.columnar.tech/dbc/getting_started/installation/)
+
+### Set up PolarDB for PostgreSQL
+
+1. [Install Docker](https://docs.docker.com/get-started/get-docker/)
+
+2. Start a PolarDB for PostgreSQL instance:
+
+    ```sh
+    docker run -d --rm --name polardb \
+        --cap-add=SYS_PTRACE --privileged=true \
+        -p 5432:5432 \
+        -e POLARDB_USER=username \
+        -e POLARDB_PASSWORD=password \
+        polardb/polardb_pg_local_instance:15
+    ```
+
+### Connect to PolarDB for PostgreSQL
+
+1. Install the PostgreSQL ADBC driver:
+
+    ```sh
+    dbc install postgresql
+    ```
+
+2. Customize the Go program `main.go` as needed
+    - Change the connection arguments in the `NewDatabase()` call
+        - Format `uri` according to the [connection URI format used by PostgreSQL](https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING-URIS), or keep it as is
+    - If you changed which database you're connecting to, also change the SQL SELECT statement in `stmt.SetSqlQuery()`
+
+3. Run the Go program:
+
+    ```sh
+    go mod tidy
+    go run main.go
+    ```
+
+### Clean up
+
+Stop the Docker container running PolarDB for PostgreSQL:
+
+```sh
+docker stop polardb
+```