fix: show create table error when using json tag

[facetosea]

Description

Please briefly describe the code changes in this pull request.

Jira: https://jira.taosdata.com:18080/browse/TD-

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[gemini-code-assist]

Summary of Changes

Hello @facetosea, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical formatting error in the SHOW CREATE TABLE command's output when dealing with tables that include JSON tags. Previously, the generated CREATE TABLE statement was syntactically incorrect due to unquoted JSON values, preventing successful table recreation. The change ensures that JSON tag values are correctly enclosed in single quotes, making the output valid and functional for recreating tables.

Highlights

• JSON Tag Formatting Fix: Resolved an issue where SHOW CREATE TABLE output for tables utilizing JSON tags would produce an invalid CREATE TABLE statement. The fix involves enclosing JSON tag values in single quotes to ensure proper syntax.

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[gemini-code-assist]

Code Review

This pull request aims to fix an issue with SHOW CREATE TABLE for tables with JSON tags by quoting the JSON string. While this is a step in the right direction, the current implementation doesn't handle single quotes within the JSON string itself, which would result in invalid SQL syntax. I've provided a suggestion to properly escape the JSON string before it's formatted to ensure the generated SQL is always valid.

[gemini-code-assist]

While adding single quotes is correct for SQL string literals, this change doesn't handle cases where the JSON string pJson itself contains single quotes. This would lead to a syntax error in the generated CREATE TABLE statement. The single quotes within the JSON string must be escaped, typically by doubling them (e.g., ' becomes '').

    // Allocate a buffer that can hold the escaped string. In the worst case, every character is a single quote.
    char* escapedJson = taosMemoryAlloc(strlen(pJson) * 2 + 1);
    if (escapedJson) {
      char* writer = escapedJson;
      for (char* reader = pJson; *reader; ++reader) {
        if (*reader == '\'') {
          *writer++ = '\''; // Escape single quote by doubling it
        }
        *writer++ = *reader;
      }
      *writer = '\0';

      *len += tsnprintf(buf + VARSTR_HEADER_SIZE + *len, SHOW_CREATE_TB_RESULT_FIELD2_LEN - (VARSTR_HEADER_SIZE + *len),
                        "'%s'", escapedJson);
      taosMemoryFree(escapedJson);
    }
    taosMemoryFree(pJson);