test_json_parser_perf.c

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/*-------------------------------------------------------------------------
 *
 * test_json_parser_perf.c
 *    Performance test program for both flavors of the JSON parser
 *
 * Copyright (c) 2024-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/test/modules/test_json_parser/test_json_parser_perf.c
 *
 * This program tests either the standard (recursive descent) JSON parser
 * or the incremental (table driven) parser, but without breaking the input
 * into chunks in the latter case. Thus it can be used to compare the pure
 * parsing speed of the two parsers. If the "-i" option is used, then the
 * table driven parser is used. Otherwise, the recursive descent parser is
 * used.
 *
 * The remaining arguments are the number of parsing iterations to be done
 * and the file containing the JSON input.
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
#include "common/jsonapi.h"
#include "common/logging.h"
#include "lib/stringinfo.h"
#include "mb/pg_wchar.h"
#include <stdio.h>
#include <string.h>
 
#define BUFSIZE 6000
 
int
main(int argc, char **argv)
{
    char        buff[BUFSIZE];
    FILE       *json_file;
    JsonParseErrorType result;
    JsonLexContext *lex;
    StringInfoData json;
    int         n_read;
    int         iter;
    int         use_inc = 0;
 
    pg_logging_init(argv[0]);
 
    initStringInfo(&json);
 
    if (strcmp(argv[1], "-i") == 0)
    {
        use_inc = 1;
        argv++;
    }
 
    sscanf(argv[1], "%d", &iter);
 
    if ((json_file = fopen(argv[2], PG_BINARY_R)) == NULL)
        pg_fatal("Could not open input file '%s': %m", argv[2]);
 
    while ((n_read = fread(buff, 1, 6000, json_file)) > 0)
    {
        appendBinaryStringInfo(&json, buff, n_read);
    }
    fclose(json_file);
    for (int i = 0; i < iter; i++)
    {
        if (use_inc)
        {
            lex = makeJsonLexContextIncremental(NULL, PG_UTF8, false);
            result = pg_parse_json_incremental(lex, &nullSemAction,
                                               json.data, json.len,
                                               true);
            freeJsonLexContext(lex);
        }
        else
        {
            lex = makeJsonLexContextCstringLen(NULL, json.data, json.len,
                                               PG_UTF8, false);
            result = pg_parse_json(lex, &nullSemAction);
            freeJsonLexContext(lex);
        }
        if (result != JSON_SUCCESS)
            pg_fatal("unexpected result %d (expecting %d) on parse",
                     result, JSON_SUCCESS);
    }
    exit(0);
}