### Build and Run Loading Example

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Provides shell commands to navigate to the loading example directory, create a database for the example, configure and build the example using CMake, and execute the compiled example program.

```sh
cd examples/loading
createdb pgvector_example
cmake -S . -B build
cmake --build build
build/example
```

--------------------------------

### Setup Development Environment and Run Tests

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Provides shell commands to clone the repository, navigate into it, create a test database, configure CMake with testing enabled, build the project, and run the tests.

```sh
git clone https://github.com/pgvector/pgvector-cpp.git
cd pgvector-cpp
createdb pgvector_cpp_test
cmake -S . -B build -DBUILD_TESTING=ON
cmake --build build
build/test
```

--------------------------------

### Install pgvector-cpp with CMake FetchContent

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Demonstrates how to integrate the pgvector-cpp library into a CMake project using FetchContent. Declares the remote repository and tag, makes it available, and links the library to a target.

```cmake
include(FetchContent)

FetchContent_Declare(pgvector GIT_REPOSITORY https://github.com/pgvector/pgvector-cpp.git GIT_TAG v0.2.2)
FetchContent_MakeAvailable(pgvector)

target_link_libraries(app PRIVATE pgvector::pgvector)
```

--------------------------------

### Get Dimensions of pgvector::SparseVector

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Retrieves the total number of dimensions defined for a `pgvector::SparseVector` object.

```cpp
int dim = vec.dimensions();
```

--------------------------------

### Get Values of Non-Zero Elements in pgvector::SparseVector

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Retrieves a vector containing the values of the non-zero elements within a `pgvector::SparseVector`.

```cpp
auto values = vec.values();
```

--------------------------------

### Get Indices of Non-Zero Elements in pgvector::SparseVector

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Retrieves a vector containing the indices of the non-zero elements within a `pgvector::SparseVector`.

```cpp
auto indices = vec.indices();
```

--------------------------------

### Enable pgvector Extension in PostgreSQL (libpqxx)

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Executes a SQL command using a libpqxx transaction object (`tx`) to create the `vector` extension in the PostgreSQL database if it doesn't already exist.

```cpp
tx.exec("CREATE EXTENSION IF NOT EXISTS vector");
```

--------------------------------

### Include pgvector libpqxx Header

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Includes the necessary header file to use pgvector functionality with the libpqxx C++ library.

```cpp
#include <pgvector/pqxx.hpp>
```

--------------------------------

### Create pgvector::HalfVector from std::vector<float>

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Demonstrates how to construct a `pgvector::HalfVector` object from a `std::vector<float>` initializer list.

```cpp
auto vec = pgvector::HalfVector({1, 2, 3});
```

--------------------------------

### Create pgvector::Vector from std::vector<float>

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Demonstrates how to construct a `pgvector::Vector` object directly from a `std::vector<float>` initializer list.

```cpp
auto vec = pgvector::Vector({1, 2, 3});
```

--------------------------------

### Query Nearest Neighbors (libpqxx)

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Executes a SQL query using a libpqxx transaction object (`tx`) to find the 5 nearest neighbors to a given `embedding` using the `<->` (L2 distance) operator and stores the result in a `pqxx::result` object.

```cpp
pqxx::result r = tx.exec("SELECT * FROM items ORDER BY embedding <-> $1 LIMIT 5", {embedding});
```

--------------------------------

### Create Table with Vector Column (libpqxx)

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Executes a SQL command using a libpqxx transaction object (`tx`) to create a table named `items` with a primary key and a `vector` column of dimension 3.

```cpp
tx.exec("CREATE TABLE items (id bigserial PRIMARY KEY, embedding vector(3))");
```

--------------------------------

### Create pgvector::SparseVector from std::unordered_map

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Shows how to construct a `pgvector::SparseVector` from a map of non-zero indices and values, specifying the total number of dimensions.

```cpp
std::unordered_map<int, float> map = {{0, 1}, {2, 2}, {4, 3}};
auto vec = pgvector::SparseVector(map, 6);
```

--------------------------------

### Insert Vector into Table (libpqxx)

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Creates a `pgvector::Vector` object from a `std::vector<float>` and inserts it into the `items` table using a parameterized SQL query via a libpqxx transaction.

```cpp
auto embedding = pgvector::Vector({1, 2, 3});
tx.exec("INSERT INTO items (embedding) VALUES ($1)", {embedding});
```

--------------------------------

### Create pgvector::SparseVector from std::vector<float>

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Demonstrates how to construct a `pgvector::SparseVector` object from a `std::vector<float>`, automatically handling zero values.

```cpp
auto vec = pgvector::SparseVector({1, 0, 2, 0, 3, 0});
```

--------------------------------

### Retrieve Vector from Table (libpqxx)

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Executes a SQL query using a libpqxx transaction object (`tx`) to select a vector from the `items` table, retrieves a single row, and casts the vector column value to a `pgvector::Vector` object.

```cpp
auto row = tx.exec("SELECT embedding FROM items LIMIT 1").one_row();
auto embedding = row[0].as<pgvector::Vector>();
```

--------------------------------

### Convert pgvector::Vector to std::vector<float>

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Shows how to cast a `pgvector::Vector` object back to its underlying `std::vector<float>` representation.

```cpp
auto float_vec = static_cast<std::vector<float>>(vec);
```

--------------------------------

### Convert pgvector::HalfVector to std::vector<float>

Source: https://github.com/pgvector/pgvector-cpp/blob/master/README.md

Shows how to cast a `pgvector::HalfVector` object back to its underlying `std::vector<float>` representation.

```cpp
auto float_vec = static_cast<std::vector<float>>(vec);
```

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