MonetDB as a shared library with a C API
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Update src/embedded/embedded.c
Latest commit 327ada7 Oct 9, 2018

README.md

MonetDBLite for C

Build StatusBuild Status

MonetDBLite is an embedded SQL database that runs inside another program and does not require the installation of any external software. MonetDBLite is based on free and open-source MonetDB, a product of the Centrum Wiskunde & Informatica.

MonetDBLite is similar in functionality to SQLite, but optimized for analytical (OLAP) use cases.

Build Process

Installation from source is a matter of typing

make -j

This produces a shared library file libmonetdb5.(so|dll|dylib) in the build/ folder, which contains all required code to run MonetDBLite. This library can then be linked to by your software. On Windows, we use the MinGW-64 toolchains (32 bit, 64 bit (recommended)) and the mingw32-make tool to build the DLL.

Usage Example

See src/embedded/embedded.h for the full API. Here a quick example

#include "embedded.h"
#include <stdio.h>

#define error(msg) {fprintf(stderr, "Failure: %s\n", msg); return -1;}

int main(void) {
	char* err = 0;
	void* conn = 0;
	monetdb_result* result = 0;
	size_t r, c;

	// first argument is a string for the db directory or NULL for in-memory mode
	err = monetdb_startup(NULL, 0, 0);
	if (err != 0)
		error(err)

	conn = monetdb_connect();
	if (conn == NULL)
		error("Connection failed")

	err = monetdb_query(conn, "CREATE TABLE test (x integer, y string)", 1,
	NULL, NULL, NULL);
	if (err != 0)
		error(err)

	err = monetdb_query(conn,
			"INSERT INTO test VALUES (42, 'Hello'), (NULL, 'World')", 1, NULL,
			NULL, NULL);
	if (err != 0)
		error(err)

	err = monetdb_query(conn, "SELECT x, y FROM test; ", 1, &result, NULL,
	NULL);
	if (err != 0)
		error(err)

	fprintf(stdout, "Query result with %d cols and %d rows\n", (int) result->ncols,
			(int) result->nrows);

	for (r = 0; r < result->nrows; r++) {
		for (c = 0; c < result->ncols; c++) {
			monetdb_column* rcol = monetdb_result_fetch(result, c);
			switch (rcol->type) {
			case monetdb_int32_t: {
				monetdb_column_int32_t * col = (monetdb_column_int32_t *) rcol;
				if (col->data[r] == col->null_value) {
					printf("NULL");
				} else {
					printf("%d", (int) col->data[r]);
				}
				break;
			}
			case monetdb_str: {
				monetdb_column_str * col = (monetdb_column_str *) rcol;
				if (col->is_null(col->data[r])) {
					printf("NULL");
				} else {
					printf("%s", (char*) col->data[r]);
				}
				break;
			}
			default: {
				printf("UNKNOWN");
			}
			}

			if (c + 1 < result->ncols) {
				printf(", ");
			}
		}
		printf("\n");
	}

	monetdb_cleanup_result(conn, result);
	monetdb_disconnect(conn);
	monetdb_shutdown();
	return 0;
}

You can build and link this example program with the MonetDBLite shared library (for example) as follows

gcc tests/readme/readme.c -o readme -Isrc/embedded -Lbuild -lmonetdb5

This should produce a binary named readme. Running this binary should produce the following output:

Query result with 2 cols and 2 rows
42, Hello
NULL, World

Issues

If you encounter a bug, please file a minimal reproducible example on github. For questions and other discussion, please use stack overflow with the tag monetdblite.