[jdbc-v2] Implements `java.sql.PreparedStatement#getMetaData` #2311

chernser · 2025-04-16T18:23:51Z

Summary

Implement java.sql.PreparedStatement#getMetaData
Returned metadata is either filled with columns (for SELECT) or an empty object with 0 columns.

Closes #2292
Closes #2311

Checklist

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Closes [jdbc-v2] Prepared statement metadata returns null #2292, [jdbc-v2] Implements java.sql.PreparedStatement#getMetaData #2311
Unit and integration tests covering the common scenarios were added
A human-readable description of the changes was provided to include in CHANGELOG
For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

…d stmt metadata

Paultagoras · 2025-04-17T08:36:50Z

jdbc-v2/src/main/java/com/clickhouse/jdbc/internal/JdbcUtils.java

+    private static Map<ClickHouseDataType, Class<?>> getDataTypeClassMap() {
+        Map<ClickHouseDataType, Class<?>> map = new HashMap<>();
+        for (Map.Entry<ClickHouseDataType, SQLType> e : CLICKHOUSE_TO_SQL_TYPE_MAP.entrySet()) {
+            map.put(e.getKey(), SQL_TYPE_TO_CLASS_MAP.get(e.getValue()));


Does this actually go the whole way from ClickHouseDataType -> SqlType -> Class?

yes, but we need to make it more bound to actual code. I mean there should be a single source of truth.

mzitnik · 2025-04-17T08:19:43Z

jdbc-v2/src/test/java/com/clickhouse/jdbc/PreparedStatementTest.java

+            assertNotNull(metadataRs);
+            assertEquals(metadataRs.getColumnCount(), colCountAfterExecution);
+            for (int i = 1; i <= metadataRs.getColumnCount(); i++) {
+                System.out.println("label=" + metadataRs.getColumnName(i) + " type=" + metadataRs.getColumnType(i));


Lets remove it

Copilot

Pull Request Overview

This PR implements the java.sql.PreparedStatement#getMetaData method to return metadata for SELECT queries (with column details) and an empty metadata object for non-SELECT queries. Key changes include:

Adding tests in PreparedStatementTest for getMetaData behavior.
Updating metadata implementations and utility methods across ResultSet, Statement, and PreparedStatement classes.
Refactoring and cleanup of unused imports and legacy metadata classes.

Reviewed Changes

Copilot reviewed 23 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
jdbc-v2/src/test/java/com/clickhouse/jdbc/StatementTest.java	Removed unused imports.
jdbc-v2/src/test/java/com/clickhouse/jdbc/PreparedStatementTest.java	Added tests and data provider for PreparedStatement#getMetaData.
jdbc-v2/src/test/java/com/clickhouse/jdbc/JdbcIntegrationTest.java	Cleaned up import statements.
jdbc-v2/src/test/java/com/clickhouse/jdbc/ConnectionTest.java	Removed unused imports.
jdbc-v2/src/main/java/com/clickhouse/jdbc/types/Array.java	Removed unused import.
jdbc-v2/src/main/java/com/clickhouse/jdbc/metadata/ResultSetMetaDataImpl.java	Refactored to use a new column list and schema properties.
jdbc-v2/src/main/java/com/clickhouse/jdbc/metadata/ParameterMetaDataImpl.java	New implementation providing minimal parameter metadata.
jdbc-v2/src/main/java/com/clickhouse/jdbc/metadata/ParameterMetaData.java	Removed legacy metadata implementation.
jdbc-v2/src/main/java/com/clickhouse/jdbc/internal/MetadataResultSet.java	Updated to instantiate the new ResultSetMetaDataImpl.
jdbc-v2/src/main/java/com/clickhouse/jdbc/internal/JdbcUtils.java	Adopted ImmutableMap for type maps and added a new replaceQuestionMarks utility.
jdbc-v2/src/main/java/com/clickhouse/jdbc/StatementImpl.java	Made slight refactoring and ensured proper schema assignment.
jdbc-v2/src/main/java/com/clickhouse/jdbc/ResultSetImpl.java	Adjusted metadata initialization and assignment.
jdbc-v2/src/main/java/com/clickhouse/jdbc/PreparedStatementImpl.java	Updated getMetaData and getParameterMetaData implementations.
client-v2/src/main/java/com/clickhouse/client/api/metadata/TableSchema.java	Removed unused imports.
.github/workflows/analysis.yml	Updated sonar command parameters.

Files not reviewed (3)

clickhouse-jdbc/pom.xml: Language not supported
client-v2/pom.xml: Language not supported
jdbc-v2/pom.xml: Language not supported

Comments suppressed due to low confidence (1)

jdbc-v2/src/main/java/com/clickhouse/jdbc/metadata/ResultSetMetaDataImpl.java:35

[nitpick] Consider performing an explicit boundary check for 'column' instead of relying on catching IndexOutOfBoundsException. This could improve readability and make the error handling more intentional.

try { return columns.get(column - 1); } catch (IndexOutOfBoundsException e) {

Copilot · 2025-04-17T08:52:38Z

jdbc-v2/src/main/java/com/clickhouse/jdbc/PreparedStatementImpl.java

        checkClosed();
-        return null;
+
+        if (resultSetMetaData == null && currentResultSet == null) {


Consider adding inline documentation clarifying that replacing question marks with 'NULL' is solely used for schema inference. This will help future maintainers understand potential limitations when the SQL contains literal question marks.

Copilot · 2025-04-17T08:52:39Z

jdbc-v2/src/main/java/com/clickhouse/jdbc/internal/JdbcUtils.java

+
+    public static final String NULL = "NULL";
+
+    private static final Pattern REPLACE_Q_MARK_PATTERN = Pattern.compile("(\"[^\"]*\"|`[^`]*`)|(\\?)");


The current regex pattern only handles double-quoted and backtick-quoted strings. Since SQL string literals are usually single-quoted, consider extending the pattern to also cover single-quoted strings to avoid unintended replacements.

Suggested change

private static final Pattern REPLACE_Q_MARK_PATTERN = Pattern.compile("(\"[^\"]*\"|`[^`]*`)|(\\?)");

private static final Pattern REPLACE_Q_MARK_PATTERN = Pattern.compile("(\"[^\"]*\"|`[^`]*`|'[^']*')|(\\?)");

Thank you! That helped a lot!

sonarqubecloud · 2025-04-17T17:50:23Z

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

chernser added 4 commits April 11, 2025 17:19

Code cleanup. Implemented dummy parameter result set. Drafted prepare…

fea9b35

…d stmt metadata

Reworked some schema staff

eb0762f

Merge branch 'main' into jdbc_prepared_stmt_metadata

07b8b1f

Implemented getting prepared statement metadata

4a93d5d

chernser requested review from Paultagoras and mzitnik and removed request for Paultagoras April 16, 2025 18:23

chernser added 6 commits April 16, 2025 13:52

fixed tests and removed unused code

6548efb

fixed minor issues

216b9f1

fixed javadoc

c51f367

fixing coverage report

cd11f52

fixing code coverage

d3edaff

push build

65572ef

chernser requested a review from Paultagoras April 17, 2025 03:36

Paultagoras reviewed Apr 17, 2025

View reviewed changes

mzitnik approved these changes Apr 17, 2025

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mshustov requested a review from Copilot April 17, 2025 08:51

Copilot AI reviewed Apr 17, 2025

View reviewed changes

Paultagoras approved these changes Apr 17, 2025

View reviewed changes

fixed bug with replacing literal '?' with NULL

3824774

chernser merged commit e62a180 into main Apr 17, 2025
24 of 25 checks passed

chernser deleted the jdbc_prepared_stmt_metadata branch April 17, 2025 18:09

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[jdbc-v2] Implements `java.sql.PreparedStatement#getMetaData` #2311

[jdbc-v2] Implements `java.sql.PreparedStatement#getMetaData` #2311

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chernser commented Apr 16, 2025 •

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		public static final String NULL = "NULL";

		private static final Pattern REPLACE_Q_MARK_PATTERN = Pattern.compile("(\"[^\"]\"\|`[^`]`)\|(\\?)");

[jdbc-v2] Implements java.sql.PreparedStatement#getMetaData #2311

[jdbc-v2] Implements java.sql.PreparedStatement#getMetaData #2311

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chernser commented Apr 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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[jdbc-v2] Implements `java.sql.PreparedStatement#getMetaData` #2311

[jdbc-v2] Implements `java.sql.PreparedStatement#getMetaData` #2311

chernser commented Apr 16, 2025 •

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