用C编写PostgreSQL函数:经典的SPI_execq示例-不打印为日志消息？

#include "postgres.h"
#include "fmgr.h"
#include "executor/spi.h"

PG_MODULE_MAGIC;

PG_FUNCTION_INFO_V1(my_function);

Datum my_function(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    int ret;
    SPI_connect();

    if (get_call_result_type(fcinfo, NULL, NULL) != TYPEFUNC_COMPOSITE)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("function returning record called in context that cannot accept type record")));

    if (SRF_IS_FIRSTCALL())
    {
        MemoryContext oldcontext;

        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        ret = SPI_exec("SELECT * FROM my_table", 0);
        if (ret < 0)
            ereport(ERROR, (errcode(ERRCODE_SPI_EXECUTE_FAILURE), errmsg("SPI_exec failed")));

        funcctx->max_calls = SPI_processed;
        MemoryContextSwitchTo(oldcontext);
    }

    funcctx = SRF_PERCALL_SETUP();
    if (funcctx->call_cntr < funcctx->max_calls)
    {
        HeapTuple tuple;
        TupleDesc tupdesc;
        Datum result;

        tupdesc = SPI_tuptable->tupdesc;
        tuple = SPI_tuptable->vals[funcctx->call_cntr];

        result = heap_copy_tuple_as_datum(tuple, tupdesc);
        SRF_RETURN_NEXT(funcctx, result);
    }
    else
    {
        SPI_finish();
        SRF_RETURN_DONE(funcctx);
    }
}