/*
 * sqlite_query.c -- steady-state query execution driver.
 *
 * Opens an already-populated database READ-ONLY and then does nothing but
 * repeatedly execute prepared queries against it. There is no CREATE, no
 * INSERT, no schema construction and no dataset loading anywhere in this
 * program; the only non-query work is sqlite3_open_v2() + sqlite3_prepare_v2()
 * at startup, a few million instructions before the steady-state loop begins.
 *
 * The database is mapped with PRAGMA mmap_size so page reads are served
 * straight out of the mapping: there is no multi-hundred-million-instruction
 * page-cache warm-up phase, the loop is in steady state almost immediately.
 *
 * The loop rotates through four query shapes, each of which exercises the
 * fixed-layout internal structures of interest:
 *   1. rowid point lookup      -> table B-tree descent, record lookup
 *   2. secondary index lookup  -> index B-tree descent + rowid table seek
 *   3. rowid range scan        -> cursor movement (sqlite3BtreeNext) over pages
 *   4. index range scan        -> index cursor movement + key comparison
 * Every iteration resets the statement, so VDBE program state management and
 * cursor teardown/re-seek are on the hot path as well.
 */
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "sqlite3.h"

static uint64_t rng;
static uint64_t next_rand(void) {
    rng = rng * 6364136223846793005ULL + 1442695040888963407ULL;
    return rng >> 17;
}

static void must(sqlite3 *db, int rc, const char *what) {
    if (rc != SQLITE_OK && rc != SQLITE_DONE && rc != SQLITE_ROW) {
        fprintf(stderr, "%s failed: %d %s\n", what, rc, sqlite3_errmsg(db));
        exit(1);
    }
}

int main(int argc, char **argv) {
    if (argc != 8) {
        fprintf(stderr,
                "usage: %s <db-path> <rounds> <n_point> <n_index> <n_range> "
                "<n_irange> <nrows>\n", argv[0]);
        return 2;
    }
    const char *path = argv[1];
    long rounds   = atol(argv[2]);
    long n_point  = atol(argv[3]);
    long n_index  = atol(argv[4]);
    long n_range  = atol(argv[5]);
    long n_irange = atol(argv[6]);
    long nrows    = atol(argv[7]);

    sqlite3 *db = NULL;
    must(db, sqlite3_open_v2(path, &db, SQLITE_OPEN_READONLY, NULL), "open");
    /* locking_mode=EXCLUSIVE takes the shared file lock once instead of
     * fcntl()-ing on every implicit read transaction; without it roughly two
     * syscalls per query dominate the profile and bury the B-tree work. */
    sqlite3_exec(db, "PRAGMA locking_mode=EXCLUSIVE;", NULL, NULL, NULL);
    sqlite3_exec(db, "PRAGMA mmap_size=2147483648;", NULL, NULL, NULL);
    sqlite3_exec(db, "PRAGMA cache_size=-524288;", NULL, NULL, NULL);
    sqlite3_exec(db, "PRAGMA query_only=ON;", NULL, NULL, NULL);

    sqlite3_stmt *q_point = NULL, *q_index = NULL, *q_range = NULL,
                 *q_irange = NULL;
    must(db, sqlite3_prepare_v2(db,
             "SELECT v0, v1, payload FROM records WHERE id = ?", -1,
             &q_point, NULL), "prepare point");
    must(db, sqlite3_prepare_v2(db,
             "SELECT id, v0 FROM records INDEXED BY idx_k WHERE k = ?", -1,
             &q_index, NULL), "prepare index");
    must(db, sqlite3_prepare_v2(db,
             "SELECT id, v0, v1 FROM records WHERE id BETWEEN ? AND ?", -1,
             &q_range, NULL), "prepare range");
    must(db, sqlite3_prepare_v2(db,
             "SELECT id, k FROM records INDEXED BY idx_k "
             "WHERE k BETWEEN ? AND ?", -1, &q_irange, NULL), "prepare irange");

    uint64_t checksum = 0;
    long rows_seen = 0;

    for (long r = 0; r < rounds; r++) {
        /* ---- phase 1: rowid point lookups (B-tree descent + record read) */
        rng = 0x1234567ULL + (uint64_t)r;
        for (long i = 0; i < n_point; i++) {
            long id = (long)(next_rand() % (uint64_t)nrows) + 1;
            sqlite3_bind_int64(q_point, 1, id);
            while (sqlite3_step(q_point) == SQLITE_ROW) {
                checksum += (uint64_t)sqlite3_column_int64(q_point, 0);
                checksum ^= (uint64_t)sqlite3_column_int64(q_point, 1);
                const unsigned char *p = sqlite3_column_text(q_point, 2);
                checksum += p ? (uint64_t)p[0] : 0;
                rows_seen++;
            }
            sqlite3_reset(q_point);
        }

        /* ---- phase 2: secondary index lookups (index descent + rowid seek) */
        rng = 0x89abcdefULL + (uint64_t)r;
        for (long i = 0; i < n_index; i++) {
            long k = (long)(next_rand() % (uint64_t)(2 * nrows));
            sqlite3_bind_int64(q_index, 1, k);
            while (sqlite3_step(q_index) == SQLITE_ROW) {
                checksum += (uint64_t)sqlite3_column_int64(q_index, 0);
                checksum ^= (uint64_t)sqlite3_column_int64(q_index, 1);
                rows_seen++;
            }
            sqlite3_reset(q_index);
        }

        /* ---- phase 3: rowid range scans (cursor movement across pages) */
        rng = 0xfeedfaceULL + (uint64_t)r;
        for (long i = 0; i < n_range; i++) {
            long lo = (long)(next_rand() % (uint64_t)(nrows - 128)) + 1;
            sqlite3_bind_int64(q_range, 1, lo);
            sqlite3_bind_int64(q_range, 2, lo + 63);
            while (sqlite3_step(q_range) == SQLITE_ROW) {
                checksum += (uint64_t)sqlite3_column_int64(q_range, 1);
                checksum ^= (uint64_t)sqlite3_column_int64(q_range, 2);
                rows_seen++;
            }
            sqlite3_reset(q_range);
        }

        /* ---- phase 4: index range scans (index cursor movement + compare) */
        rng = 0xdeadbeefULL + (uint64_t)r;
        for (long i = 0; i < n_irange; i++) {
            long lo = (long)(next_rand() % (uint64_t)(2 * nrows - 256));
            sqlite3_bind_int64(q_irange, 1, lo);
            sqlite3_bind_int64(q_irange, 2, lo + 127);
            while (sqlite3_step(q_irange) == SQLITE_ROW) {
                checksum += (uint64_t)sqlite3_column_int64(q_irange, 0);
                checksum ^= (uint64_t)sqlite3_column_int64(q_irange, 1);
                rows_seen++;
            }
            sqlite3_reset(q_irange);
        }
    }

    sqlite3_finalize(q_point);
    sqlite3_finalize(q_index);
    sqlite3_finalize(q_range);
    sqlite3_finalize(q_irange);
    sqlite3_close(db);
    fprintf(stderr, "rows=%ld checksum=%llu\n", rows_seen,
            (unsigned long long)checksum);
    return 0;
}