poc.c Local execution arking.

Certainly! Let's break down the code step by step. This code is written in C and is used to define a custom PostgreSQL function.

Explanation in Markdown Format

1. Include Necessary Headers

#include "postgres.h"
#include <string.h>
#include "fmgr.h"
#include "utils/geo_decls.h"
#include <stdio.h>
#include "utils/builtins.h"

2. Module Magic

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

This part is required for PostgreSQL to recognize the module.

3. Function Declaration

/* Add a prototype marked PGDLLEXPORT */
PGDLLEXPORT Datum awae(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(awae);

4. Function Definition

Datum
awae(PG_FUNCTION_ARGS)
{
    /* convert text pointer to C string */
    #define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))

5. Retrieve and Use Arguments

    /* retrieve the second argument that is passed to the function (an integer)
    that will serve as our counter limit*/

    int instances = PG_GETARG_INT32(1);

    for (int c = 0; c < instances; c++) {
        /*launch the process passed in the first parameter*/
        ShellExecute(NULL, "open", GET_STR(PG_GETARG_TEXT_P(0)), NULL, NULL, 1);
    }
    PG_RETURN_VOID();
}

Full Code

#include "postgres.h"
#include <string.h>
#include "fmgr.h"
#include "utils/geo_decls.h"
#include <stdio.h>
#include "utils/builtins.h"

#ifdef PG_MODULE_MAGIC

postgres.h: Core PostgreSQL definitions.
string.h: Standard C library for string functions.
fmgr.h: Definitions for PostgreSQL function manager.
utils/geo_decls.h: Geographic data type declarations.
stdio.h: Standard C library for input and output functions.
utils/builtins.h: Built-in PostgreSQL functions.

PG_MODULE_MAGIC;
#endif

This part is required for PostgreSQL to recognize the module.

/* Add a prototype marked PGDLLEXPORT */
PGDLLEXPORT Datum awae(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(awae);

PGDLLEXPORT Datum awae(PG_FUNCTION_ARGS);: Declares the function awae.
PG_FUNCTION_INFO_V1(awae);: Registers the function with PostgreSQL.

/* this function launches the executable passed in as the first parameter
in a FOR loop bound by the second parameter that is also passed*/
Datum
awae(PG_FUNCTION_ARGS)
{
    /* convert text pointer to C string */
    #define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))

Datum: PostgreSQL data type for returning values.
PG_FUNCTION_ARGS: Macro that provides access to function arguments.
GET_STR(textp): Macro to convert PostgreSQL text to C string.

    /* retrieve the second argument that is passed to the function (an integer)
    that will serve as our counter limit*/

    int instances = PG_GETARG_INT32(1);

    for (int c = 0; c < instances; c++) {
        /*launch the process passed in the first parameter*/
        ShellExecute(NULL, "open", GET_STR(PG_GETARG_TEXT_P(0)), NULL, NULL, 1);
    }
    PG_RETURN_VOID();
}

int instances = PG_GETARG_INT32(1);: Retrieves the second argument as an integer, which serves as the counter limit.
for (int c = 0; c < instances; c++): Loop that runs from 0 to instances - 1.
ShellExecute(NULL, "open", GET_STR(PG_GETARG_TEXT_P(0)), NULL, NULL, 1);: Executes the command passed as the first argument in each loop iteration.
PG_RETURN_VOID();: Indicates that the function returns no value.

This code defines a PostgreSQL function that takes two arguments: a command to execute and a number of times to execute it. It then runs the command the specified number of times.

#include "postgres.h"
#include <string.h>
#include "fmgr.h"
#include "utils/geo_decls.h"
#include <stdio.h>
#include "utils/builtins.h"

#ifdef PG_MODULE_MAGIC
PG_MODULE_MAGIC;
#endif

/* Add a prototype marked PGDLLEXPORT */
PGDLLEXPORT Datum awae(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(awae);

/* this function launches the executable passed in as the first parameter
in a FOR loop bound by the second parameter that is also passed*/
Datum
awae(PG_FUNCTION_ARGS)
{
    /* convert text pointer to C string */
    #define GET_STR(textp) DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))

    /* retrieve the second argument that is passed to the function (an integer)
    that will serve as our counter limit*/

    int instances = PG_GETARG_INT32(1);

    for (int c = 0; c < instances; c++) {
        /*launch the process passed in the first parameter*/
        ShellExecute(NULL, "open", GET_STR(PG_GETARG_TEXT_P(0)), NULL, NULL, 1);
    }
    PG_RETURN_VOID();
}