去掉冗余数据

remove_data.php

<?php
    $servername = "";
    $username = "";
    $password = "";
    $conn = new PDO("mysql:host=$servername;dbname=steemdb", $username, $password);

    $i = 2508;
    $end = 3263402; // 3263402
    $step = 100;

    while ($i <= $end) {
        $tmp_end = $i + $step;
        $sql = "select block_num, block_info from blocks where block_num >= {$i} and block_num <= {$tmp_end}";
        $sth = $conn->prepare($sql);
        $sth->execute();
        $res = $sth->fetchAll();
        var_dump($i, $tmp_end, $res);
        echo "\n";

        $update_sql = "update blocks set block_info = case block_num ";
        $tmp_block_num = [];
        foreach($res as $k => $v) {
            $tmp_info = $v['block_info'];
            $tmp_info = json_decode($tmp_info, true);
            if (isset($tmp_info['previous'])) {
                unset($tmp_info['previous']);
            }
            if (isset($tmp_info['timestamp'])) {
                unset($tmp_info['timestamp']);
            }
            if (isset($tmp_info['block_id'])) {
                unset($tmp_info['block_id']);
            }
            if (isset($tmp_info['block_num'])) {
                unset($tmp_info['block_num']);
            }
            $tmp_info = json_encode($tmp_info);
            $update_sql .= " when {$v['block_num']} then '{$tmp_info}' ";
            array_push($tmp_block_num, $v['block_num']);
        }
        $tmp_block_num_str = implode(',', $tmp_block_num);
        $update_sql .= " end where block_num in ({$tmp_block_num_str})";
        echo $update_sql."\n\n";
        $conn->exec($update_sql);
        $i = $tmp_end + 1;
    }