Function overflowize_index_cell

internal/cbm/sqlite_writer.c:1105–1127

If an index cell's payload exceeds X, rewrite it to spill the tail to overflow pages: varint(payload_len) + payload[0..local) + u32(first_ovfl). Returns the (possibly new, malloc'd) cell; frees the original when replaced.

// overflow pages: varint(payload_len) + payload[0..local) + u32(first_ovfl).
// Returns the (possibly new, malloc'd) cell; frees the original when replaced.
static uint8_t *overflowize_index_cell(FILE *fp, uint32_t *next_page, uint8_t *cell,
                                       int *cell_len) {
    uint64_t plen = 0;
    int vlen = get_varint(cell, &plen);
    if ((int64_t)plen <= INDEX_OVERFLOW_MAX_LOCAL) {
        return cell;
    }
    int64_t per_ovfl = (int64_t)CBM_PAGE_SIZE - BTREE_PTR_SIZE;
    int64_t k = INDEX_OVERFLOW_MIN_LOCAL + (((int64_t)plen - INDEX_OVERFLOW_MIN_LOCAL) % per_ovfl);
    int local = (k <= INDEX_OVERFLOW_MAX_LOCAL) ? (int)k : INDEX_OVERFLOW_MIN_LOCAL;
    uint32_t first_ovfl =
        write_overflow_pages(fp, next_page, cell + vlen + local, (int)plen - local);
    int nlen = vlen + local + BTREE_PTR_SIZE;
    uint8_t *data = (uint8_t *)malloc((size_t)nlen);
    if (!data) {
        return cell; /* fall back to the (broken) inline form on OOM */
    }
    memcpy(data, cell, (size_t)(vlen + local));
    put_u32(data + vlen + local, first_ovfl);
    free(cell);
    *cell_len = nlen;
    return data;
}
#define TABLE_OVERFLOW_MIN_LOCAL 8199

// Add a table cell to the PageBuilder, flushing leaf pages as needed.