[GitHub] [shardingsphere] FakeKotaro opened a new issue, #25192: Some questions about SQL parsing cache

["FakeKotaro (via GitHub)" <gi...@apache.org>]

FakeKotaro opened a new issue, #25192:
URL: https://github.com/apache/shardingsphere/issues/25192

   I've been using Sharding-JDBC's encryption feature and have recently been working on SQL parsing and rewriting performance. In version 4.1.0, SQL parsing has only one layer of cache, the structure is <sql, SqlStatement>
   ```java
   private SQLStatement parse0(final String sql, final boolean useCache) {
           if (useCache) {
               Optional<SQLStatement> cachedSQLStatement = cache.getSQLStatement(sql);
               if (cachedSQLStatement.isPresent()) {
                   return cachedSQLStatement.get();
               }
           }
           ParseTree parseTree = new SQLParserExecutor(databaseTypeName, sql).execute().getRootNode();
           SQLStatement result = (SQLStatement) ParseTreeVisitorFactory.newInstance(databaseTypeName, VisitorRule.valueOf(parseTree.getClass())).visit(parseTree);
           if (useCache) {
               cache.put(sql, result);
           }
           return result;
       }
   ```
   In the new version, a separate layer of caching has been added for parsing: <sql, ParseASTNode>.
   ```java
   public ParseASTNode parse(final String sql, final boolean useCache) {
           return useCache ? parseTreeCache.get(sql) : sqlParserExecutor.parse(sql);
       }
   ```
   My question is:
   1. Why add a separate layer of caching for parsing
   2. Why not add a layer of caching for rewrites, structured as <originSql, rewrittenSql>. Taking the encryption function as an example, the cache is < "SELECT name FROM user","SELECT name_encode as name FROM user">, so that the cache can be queried when the original SQL statement is received, and there is no need to go through the process of parsing and visiting
   3. I found that the first execution of SQL statements is slow, some complex SQL in local tests even reached 100ms latency, is this normal or is there a way to speed up the first execution?
   
   


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[GitHub] [shardingsphere] tuichenchuxin commented on issue #25192: Some questions about SQL parsing cache

["tuichenchuxin (via GitHub)" <gi...@apache.org>]

tuichenchuxin commented on issue #25192:
URL: https://github.com/apache/shardingsphere/issues/25192#issuecomment-1515602969

   The first execution requires parsing and is indeed slightly slower. The main slow point is parsing, so only caching is added for parsing.


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