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C Native API

1. Overview

The C Native API (SessionC) is a C language wrapper for the C++ Session SDK. It is used in the same way as the C++ driver. You only need to include the additional header file SessionC.h. Compilation, linking, and runtime deployment share the same iotdb_session shared library as the C++ driver.

Thrift and Boost are already packaged into iotdb_session. Applications do not need to install Thrift or Boost headers/libraries separately.

Note: This feature is supported since V2.0.10.

2. Installation

2.1 Option 1: Use the precompiled SDK package (recommended)

CI publishes zip packages by platform/toolchain. The file name is in the form iotdb-session-cpp-<version>-<classifier>.zip. After extraction, the directory structure is as follows:

iotdb-session-cpp-<version>-<classifier>/
├── include/
│   ├── SessionC.h          # C Native API header file
│   ├── Session.h           # C++ API header file
│   └── ...
├── lib/
│   ├── libiotdb_session.so       # Linux
│   ├── libiotdb_session.dylib      # macOS
│   └── iotdb_session.dll + .lib    # Windows
├── cmake/iotdb-session-config.cmake
├── pkgconfig/iotdb-session.pc
└── examples/                       # Includes table_example.c

Select the classifier according to the target environment:

Target environment classifier suffix
Linux x86_64, glibc >= 2.28 linux-x86_64-glibc2.28
Linux aarch64, glibc >= 2.28 linux-aarch64-glibc2.28
macOS x86_64 macos-x86_64
macOS arm64 macos-aarch64
Windows + Visual Studio 2017 windows-x86_64-msvc14.1
Windows + Visual Studio 2019 windows-x86_64-msvc14.2
Windows + Visual Studio 2022 windows-x86_64-msvc14.3
Windows + Visual Studio 2026 windows-x86_64-msvc14.4

Note: Do not use a higher-version client to connect to a lower-version server.

2.1.1 C program compilation example

Linux / macOS:

gcc -std=c11 table_example.c \
  -I"$IOTDB_SESSION_HOME/include" \
  -L"$IOTDB_SESSION_HOME/lib" \
  -liotdb_session -pthread \
  -Wl,-rpath,"$IOTDB_SESSION_HOME/lib" \
  -o table_example

Windows + MSVC:

Compile in the x64 Native Tools Command Prompt (or run vcvars64.bat first to initialize the environment):

set IOTDB_SESSION_HOME=C:\path\to\iotdb-session-cpp-<version>-<classifier>
cd /d %IOTDB_SESSION_HOME%\examples
cl /TC /std:c11 table_example.c /I "%IOTDB_SESSION_HOME%\include" ^
  /link /LIBPATH:"%IOTDB_SESSION_HOME%\lib" iotdb_session.lib
copy /Y "%IOTDB_SESSION_HOME%\lib\iotdb_session.dll" .

At runtime, place libiotdb_session.so / .dylib / .dll in the same directory as the executable, or configure the corresponding dynamic library search path for your platform.

2.1.2 Compile examples in the SDK package

Run the following commands in the root directory of the extracted SDK package. The examples/ directory must be at the same level as include/ and lib/.

cd iotdb-session-cpp-<version>-<classifier>
cmake -S examples -B examples-build -DCMAKE_BUILD_TYPE=Release
cmake --build examples-build

Windows + Visual Studio:

cd iotdb-session-cpp-<version>-<classifier>
cmake -S examples -B examples-build -G "Visual Studio 17 2022" -A x64
cmake --build examples-build --config Release

If the library is installed in another path, such as the source CMake installation directory iotdb-client/client-cpp/target/install, explicitly specify IOTDB_SDK_ROOT. This directory must contain include/ and lib/.

cmake -S iotdb-client/client-cpp/examples -B examples-build -DCMAKE_BUILD_TYPE=Release \
  -DIOTDB_SDK_ROOT=iotdb-client/client-cpp/target/install
cmake --build examples-build

Windows example:

cmake -S iotdb-client\client-cpp\examples -B examples-build -G "Visual Studio 17 2022" -A x64 ^
  -DIOTDB_SDK_ROOT=D:\iotdb\iotdb-client\client-cpp\target\install
cmake --build examples-build --config Release --target table_example

2.2 Option 2: Build from source

2.2.1 Install build dependencies (required only for source builds)

  • macOS
brew install bison boost openssl
  • Ubuntu 16.04+ or other Debian distributions
sudo apt-get update
sudo apt-get install gcc g++ bison flex libboost-all-dev libssl-dev cmake
  • CentOS 7.7+/Fedora/Rocky Linux or other Red Hat distributions
sudo yum update
sudo yum install gcc gcc-c++ boost-devel bison flex openssl-devel cmake
  • Windows
  1. Install MS Visual Studio (2019+ recommended), and select the C/C++ IDE and compiler components with CMake support.

  2. Install CMake.

  3. Install Win_Flex_Bison, rename the executables to flex.exe and bison.exe, and add them to PATH.

  4. Install Boost (optional, CMake can also fetch it automatically) and OpenSSL.

    The CMake build compiles Thrift 0.23 from source. SSL is enabled by default. If system OpenSSL cannot be found, the build falls back to building OpenSSL from source.

2.2.2 Build

Clone the source code from git:

git clone https://github.com/apache/iotdb.git
cd iotdb

To use a specific release version, switch to the corresponding branch, such as 2.0.6:

git checkout rc/2.0.6

Run the Maven build in the IoTDB root directory (recommended):

# Linux / macOS: build and package the SDK
./mvnw -P with-cpp -pl iotdb-client/client-cpp -am -DskipTests package

# Windows (Visual Studio 2022 example)
.\mvnw.cmd -P with-cpp -pl iotdb-client/client-cpp -am -DskipTests package

If Boost is not added to PATH on Windows, append a parameter such as:

-Dboost.include.dir="C:\boost_1_88_0"

You can also use CMake directly:

cmake -S iotdb-client/client-cpp -B build
cmake --build build --target install

Linux release packages are built in the manylinux_2_28 container. The target machine requires glibc 2.28 or later. The current build no longer uses old parameters such as -Diotdb-tools-thrift.version=0.14.1.1-gcc4-SNAPSHOT.

Full verification with integration tests:

./mvnw clean verify -P with-cpp -pl iotdb-client/client-cpp -am

2.3 Build artifacts

After a successful build, C API related files are located as follows:

  • C API header file (source): iotdb-client/client-cpp/src/include/SessionC.h

  • C API header file (installation/SDK package): include/SessionC.h

  • Library files:

    • Source build: iotdb-client/client-cpp/target/install/lib/

    • Maven package: iotdb-client/client-cpp/target/iotdb-session-cpp-<version>-<classifier>.zip

    • Linux: lib/libiotdb_session.so

    • Windows: lib/iotdb_session.dll / lib/iotdb_session.lib

  • Example source code:

    • Tree model: iotdb-client/client-cpp/examples/table_example.c

    • Table model: iotdb-client/client-cpp/examples/table_example.c

  • Integration tests:

    • Tree model: iotdb-client/client-cpp/test/cpp/sessionCIT.cpp

    • Table model: iotdb-client/client-cpp/test/cpp/sessionCRelationalIT.cpp

3. Basic API description

Description: The C driver is used in the same way as the C++ driver. You only need to include the additional header file SessionC.h. Compilation, runtime behavior, and system dependencies are shared with the C++ driver.

3.1 Common conventions

3.1.1 Status codes and error messages

  • TsStatus: TS_OK (0) indicates success. Any non-zero value indicates failure.

  • Predefined error codes:

    • TS_ERR_CONNECTION (-1)

    • TS_ERR_EXECUTION (-2)

    • TS_ERR_INVALID_PARAM (-3)

    • TS_ERR_NULL_PTR (-4)

    • TS_ERR_UNKNOWN (-99)

  • The implementation may also return other negative values, which must be interpreted together with ts_get_last_error().

  • The Session C++ API reports many errors through exceptions and does not return a unified status code. The C API uniformly returns the integer type TsStatus, and fine-grained error information can be obtained through ts_get_last_error().

const char* ts_get_last_error(void);

Returns the error message of the last failed C API call in the current thread. The returned pointer is valid until the next C API call in the same thread.

3.1.2 Memory and handle rules

  • All char* buf + int bufLen output parameters must be allocated by the caller.

  • CTableSession*, CTablet*, CSessionDataSet*, and CRowRecord* are opaque pointers. After successful creation, the caller must release them according to the conventions of each API.

3.2 Enumerations and constants

  • TSDataType_C (data type)
Enumeration value Meaning
TS_TYPE_BOOLEAN Boolean
TS_TYPE_INT32 32-bit integer
TS_TYPE_INT64 64-bit integer
TS_TYPE_FLOAT Single-precision floating point
TS_TYPE_DOUBLE Double-precision floating point
TS_TYPE_TEXT Text
TS_TYPE_TIMESTAMP Timestamp
TS_TYPE_DATE Date
TS_TYPE_BLOB Binary large object
TS_TYPE_STRING String
TS_TYPE_INVALID Invalid parameter/error path (not a server-side type)
  • TSEncoding_C (encoding)

TS_ENCODING_PLAIN, TS_ENCODING_DICTIONARY, TS_ENCODING_RLE, TS_ENCODING_DIFF, TS_ENCODING_TS_2DIFF, TS_ENCODING_BITMAP, TS_ENCODING_GORILLA_V1, TS_ENCODING_REGULAR, TS_ENCODING_GORILLA, TS_ENCODING_ZIGZAG, TS_ENCODING_FREQ

  • TSCompressionType_C (compression)

TS_COMPRESSION_UNCOMPRESSED, TS_COMPRESSION_SNAPPY, TS_COMPRESSION_GZIP, TS_COMPRESSION_LZO, TS_COMPRESSION_SDT, TS_COMPRESSION_PAA, TS_COMPRESSION_PLA, TS_COMPRESSION_LZ4, TS_COMPRESSION_ZSTD, TS_COMPRESSION_LZMA2

  • TSColumnCategory_C (table model column category)
Enumeration value Meaning
TS_COL_TAG TAG column
TS_COL_FIELD FIELD column
TS_COL_ATTRIBUTE ATTRIBUTE column

3.3 Handles, status codes, and constants

Name C definition Meaning Lifecycle responsibility
CTableSession* typedef struct CTableSession_ CTableSession; Table model session After ts_table_session_new / ts_table_session_new_multi_node succeeds, the caller calls ts_table_session_close if it has been opened, and then ts_table_session_destroy
CTablet* typedef struct CTablet_ CTablet; (opaque) Tablet batch writing, shared by tree and table models After ts_tablet_new / ts_tablet_new_with_category succeeds, the caller calls ts_tablet_destroy
CSessionDataSet* typedef struct CSessionDataSet_ CSessionDataSet; (opaque) Query result set, shared by tree and table models After a query API successfully returns *dataSet, the caller calls ts_dataset_destroy
CRowRecord* typedef struct CRowRecord_ CRowRecord; (opaque) Current row When ts_dataset_next returns a non-null value, the caller calls ts_row_record_destroy
TsStatus typedef int64_t TsStatus; API execution result code TS_OK is 0. Any non-zero value indicates failure
ts_get_last_error const char* ts_get_last_error(void); Error message of the last failed C API call in the current thread
The returned pointer is valid until the next C API call in the same thread

3.4 Common Tablet APIs

3.4.1 Creation and destruction

API signature Function Input parameters Return value Success condition Failure condition Resource responsibility
CTablet* ts_tablet_new(const char* deviceId, int columnCount, const char* const* columnNames, const TSDataType_C* dataTypes, int maxRowNumber); Create a Tablet handle deviceId: device or table name; columnNames / dataTypes: arrays of column names and types; maxRowNumber: maximum number of rows CTablet* Returns a non-null handle Returns a null handle Caller calls ts_tablet_destroy
CTablet* ts_tablet_new_with_category(const char* deviceId, int columnCount, const char* const* columnNames, const TSDataType_C* dataTypes, const TSColumnCategory_C* columnCategories, int maxRowNumber); Create a Tablet with column categories (TAG/FIELD/ATTRIBUTE) columnCategories: TS_COL_TAG / TS_COL_FIELD / TS_COL_ATTRIBUTE CTablet* Returns a non-null handle Returns a null handle Caller calls ts_tablet_destroy
void ts_tablet_destroy(CTablet* tablet); Destroy a Tablet handle tablet: handle to release None The handle must not be used after the call - Releases tablet

3.4.2 Data filling and state control

API signature Function Return value Success condition Remarks
int ts_tablet_get_row_count(CTablet* tablet); Query the current valid row count of the Tablet int Row count >= 0 Read-only query
TsStatus ts_tablet_set_row_count(CTablet* tablet, int rowCount); Set the valid row count of the Tablet TsStatus TS_OK The valid row count must be set before writing
TsStatus ts_tablet_add_timestamp(CTablet* tablet, int rowIndex, int64_t timestamp); Write a timestamp for the specified row TsStatus TS_OK
TsStatus ts_tablet_add_value_bool(CTablet* tablet, int colIndex, int rowIndex, bool value); Write a Boolean value TsStatus TS_OK
TsStatus ts_tablet_add_value_int32(CTablet* tablet, int colIndex, int rowIndex, int32_t value); Write an int32 value TsStatus TS_OK
TsStatus ts_tablet_add_value_int64(CTablet* tablet, int colIndex, int rowIndex, int64_t value); Write an int64 value TsStatus TS_OK
TsStatus ts_tablet_add_value_float(CTablet* tablet, int colIndex, int rowIndex, float value); Write a float value TsStatus TS_OK
TsStatus ts_tablet_add_value_double(CTablet* tablet, int colIndex, int rowIndex, double value); Write a double value TsStatus TS_OK
TsStatus ts_tablet_add_value_string(CTablet* tablet, int colIndex, int rowIndex, const char* value); Write a string TsStatus TS_OK String memory is managed by the caller
void ts_tablet_reset(CTablet* tablet); Reset the internal state of the Tablet for reuse void - Does not release the object. Only clears the state

Description: The current SessionC implementation does not provide ts_tablet_add_value_object. Use the C++ Session API to write OBJECT values.

3.5 Common DataSet APIs

3.5.1 Iteration control and metadata

API signature Function Return value Remarks
void ts_dataset_set_fetch_size(CSessionDataSet* dataSet, int fetchSize); Set the fetch batch size of the result set None
bool ts_dataset_has_next(CSessionDataSet* dataSet); Determine whether there may be another row bool On failure, check ts_get_last_error()
CRowRecord* ts_dataset_next(CSessionDataSet* dataSet); Get the next row record handle Row handle pointer Non-NULL indicates a valid row. NULL indicates end or failure
int ts_dataset_get_column_count(CSessionDataSet* dataSet); Get the number of columns in the result set int
const char* ts_dataset_get_column_name(CSessionDataSet* dataSet, int index); Get a column name by index String pointer No buf/bufLen output
const char* ts_dataset_get_column_type(CSessionDataSet* dataSet, int index); Get a column type name by index Type name string pointer No buf/bufLen output
void ts_dataset_destroy(CSessionDataSet* dataSet); Release a query result set handle None After each non-null CRowRecord* returned by ts_dataset_next, call ts_row_record_destroy in time

3.5.2 Value access

API signature Function Return value Remarks
void ts_row_record_destroy(CRowRecord* record); Release a row record handle None
int64_t ts_row_record_get_timestamp(CRowRecord* record); Read the timestamp of the current row int64_t The timestamp is not read from DataSet
int ts_row_record_get_field_count(CRowRecord* record); Read the number of fields in the current row int
bool ts_row_record_is_null(CRowRecord* record, int index); Determine whether the specified column is null bool
bool ts_row_record_get_bool(CRowRecord* record, int index); Read a Boolean value by column index bool
int32_t ts_row_record_get_int32(CRowRecord* record, int index); Read an int32 value by column index int32_t
int64_t ts_row_record_get_int64(CRowRecord* record, int index); Read an int64 value by column index int64_t
float ts_row_record_get_float(CRowRecord* record, int index); Read a float value by column index float
double ts_row_record_get_double(CRowRecord* record, int index); Read a double value by column index double
const char* ts_row_record_get_string(CRowRecord* record, int index); Read the byte view of a text/binary column const char. May contain .. Not a buf . bufLen pattern
int32_t ts_row_record_get_date_int32(CRowRecord* record, int index); Read a DATE column and return an integer in YYYYMMDD format int32_t Returns 0 if the field is null, out of bounds, or not DATE
size_t ts_row_record_get_string_byte_length(CRowRecord* record, int index); Read the byte length of a string/binary field size_t TEXT/BLOB/STRING, etc. Do not use strlen
TSDataType_C ts_row_record_get_data_type(CRowRecord* record, int index); Read the data type enumeration by column index Enumeration Returns TS_TYPE_INVALID for invalid parameters or out-of-bounds indexes

3.6 Table model CTableSession API matrix

3.6.1 Lifecycle

API signature Function Return value Resource responsibility
CTableSession* ts_table_session_new(const char* host, int rpcPort, const char* username, const char* password, const char* database); Create a table model session CTableSession* If opened, call ts_table_session_close first, and then ts_table_session_destroy
CTableSession* ts_table_session_new_multi_node(const char* const* nodeUrls, int urlCount, const char* username, const char* password, const char* database); Create a table model session (multi-node URL) CTableSession* Same as above
TsStatus ts_table_session_open(CTableSession* session); Open a table model RPC connection TsStatus On failure, check ts_get_last_error()
TsStatus ts_table_session_close(CTableSession* session); Close a table model connection TsStatus ts_table_session_destroy is still required
void ts_table_session_destroy(CTableSession* session); Destroy a table model session handle None Releases session

Description: The database parameter is the default database name. Pass the empty string "" to leave it unset, and switch later through the USE SQL statement.

3.6.2 Writing and querying

API signature Function Return value Resource responsibility
TsStatus ts_table_session_insert(CTableSession* session, CTablet* tablet); Write data by Tablet in the table model TsStatus Ownership of tablet is not transferred
TsStatus ts_table_session_execute_query(CTableSession* session, const char* sql, CSessionDataSet** dataSet); Execute query SQL in the table model TsStatus Caller calls ts_dataset_destroy for *dataSet
TsStatus ts_table_session_execute_query_with_timeout(CTableSession* session, const char* sql, int64_t timeoutInMs, CSessionDataSet** dataSet); Execute a query with timeout in the table model TsStatus Same as above
TsStatus ts_table_session_execute_non_query(CTableSession* session, const char* sql); Execute non-query SQL in the table model TsStatus No new handle

4. Sample code

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "SessionC.h"

#define HOST "127.0.0.1"
#define PORT 6667
#define USER "root"
#define PASS "root"

#define DB_NAME "cdemo_db"
#define TABLE_NAME "cdemo_t0"

static void fail(const char* ctx, CTableSession* s) {
  fprintf(stderr, "[table_example] %s failed: %s.", ctx, ts_get_last_error());
  if (s) {
    ts_table_session_close(s);
    ts_table_session_destroy(s);
  }
  exit(1);
}

int main(void) {
  /* The last parameter is the default database name. Pass "" to leave it unset and switch later through USE SQL. */
  CTableSession* session = ts_table_session_new(HOST, PORT, USER, PASS, "");
  if (!session) {
    fprintf(stderr, "[table_example] ts_table_session_new returned NULL: %s.",
            ts_get_last_error());
    return 1;
  }
  if (ts_table_session_open(session) != TS_OK) {
    fail("ts_table_session_open", session);
  }

  char sql[512];
  snprintf(sql, sizeof(sql), "DROP DATABASE IF EXISTS %s", DB_NAME);
  (void)ts_table_session_execute_non_query(session, sql);

  snprintf(sql, sizeof(sql), "CREATE DATABASE %s", DB_NAME);
  if (ts_table_session_execute_non_query(session, sql) != TS_OK) {
    fail("CREATE DATABASE", session);
  }

  snprintf(sql, sizeof(sql), "USE .%s.", DB_NAME);
  if (ts_table_session_execute_non_query(session, sql) != TS_OK) {
    fail("USE DATABASE", session);
  }

  const char* ddl = "CREATE TABLE " TABLE_NAME " ("
                    "tag1 string tag,"
                    "attr1 string attribute,"
                    "m1 double field)";
  if (ts_table_session_execute_non_query(session, ddl) != TS_OK) {
    fail("CREATE TABLE", session);
  }

  const char* columnNames[] = {"tag1", "attr1", "m1"};
  TSDataType_C dataTypes[] = {TS_TYPE_STRING, TS_TYPE_STRING, TS_TYPE_DOUBLE};
  TSColumnCategory_C colCategories[] = {TS_COL_TAG, TS_COL_ATTRIBUTE, TS_COL_FIELD};

  CTablet* tablet =
      ts_tablet_new_with_category(TABLE_NAME, 3, columnNames, dataTypes, colCategories, 100);
  if (!tablet) {
    fail("ts_tablet_new_with_category", session);
  }

  int i;
  for (i = 0; i < 5; i++) {
    if (ts_tablet_add_timestamp(tablet, i, (int64_t)i) != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_timestamp", session);
    }
    if (ts_tablet_add_value_string(tablet, 0, i, "device_A") != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_string tag", session);
    }
    if (ts_tablet_add_value_string(tablet, 1, i, "attr_val") != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_string attr", session);
    }
    if (ts_tablet_add_value_double(tablet, 2, i, (double)i * 1.5) != TS_OK) {
      ts_tablet_destroy(tablet);
      fail("ts_tablet_add_value_double", session);
    }
  }
  if (ts_tablet_set_row_count(tablet, 5) != TS_OK) {
    ts_tablet_destroy(tablet);
    fail("ts_tablet_set_row_count", session);
  }

  if (ts_table_session_insert(session, tablet) != TS_OK) {
    ts_tablet_destroy(tablet);
    fail("ts_table_session_insert", session);
  }
  ts_tablet_destroy(tablet);

  CSessionDataSet* dataSet = NULL;
  if (ts_table_session_execute_query(session, "SELECT * FROM " TABLE_NAME, &dataSet) != TS_OK) {
    fail("ts_table_session_execute_query", session);
  }
  if (!dataSet) {
    fprintf(stderr, "[table_example] dataSet is NULL.");
    ts_table_session_close(session);
    ts_table_session_destroy(session);
    return 1;
  }
  ts_dataset_set_fetch_size(dataSet, 1024);

  int count = 0;
  while (ts_dataset_has_next(dataSet)) {
    CRowRecord* record = ts_dataset_next(dataSet);
    if (!record) {
      break;
    }
    printf("[table_example] row %d: time=%lld.", count,
           (long long)ts_row_record_get_timestamp(record));
    ts_row_record_destroy(record);
    count++;
  }
  ts_dataset_destroy(dataSet);
  printf("[table_example] SELECT returned %d row(s)..", count);

  snprintf(sql, sizeof(sql), "DROP DATABASE IF EXISTS %s", DB_NAME);
  (void)ts_table_session_execute_non_query(session, sql);

  ts_table_session_close(session);
  ts_table_session_destroy(session);
  return 0;
}