Add text-to-sql module: schema prompt through a restricted role, JSqlParser guard, read-only role with column grants and timeout, row cap, execution-based evaluation on a real PostgreSQL

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01JXVi2GMQ7bR5EmbUFdDj7N

text-to-sql/src/main/java/com/ankurm/texttosql/SchemaPrompt.java

@@ -0,0 +1,71 @@
+package com.ankurm.texttosql;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Builds the schema section of the prompt from the database itself (information_schema plus the
+ * COMMENTs on tables and columns), for an explicit list of tables. A table that is not in the list
+ * is not described, so the model is never shown that it exists.
+ */
+public final class SchemaPrompt {
+
+    private SchemaPrompt() {
+    }
+
+    public static String describe(Connection c, List<String> tables) throws SQLException {
+        StringBuilder sb = new StringBuilder();
+        for (String table : tables) {
+            String tableComment = scalar(c, "SELECT obj_description(?::regclass, 'pg_class')", table);
+            sb.append("TABLE ").append(table);
+            if (tableComment != null) {
+                sb.append("  -- ").append(tableComment);
+            }
+            sb.append('\n');
+            try (PreparedStatement ps = c.prepareStatement(
+                    "SELECT column_name, data_type, col_description(?::regclass, ordinal_position) "
+                            + "FROM information_schema.columns WHERE table_schema = 'public' AND table_name = ? "
+                            + "ORDER BY ordinal_position")) {
+                ps.setString(1, table);
+                ps.setString(2, table);
+                try (ResultSet rs = ps.executeQuery()) {
+                    while (rs.next()) {
+                        sb.append("  ").append(rs.getString(1)).append(' ').append(rs.getString(2));
+                        if (rs.getString(3) != null) {
+                            sb.append("  -- ").append(rs.getString(3));
+                        }
+                        sb.append('\n');
+                    }
+                }
+            }
+        }
+        return sb.toString();
+    }
+
+    private static String scalar(Connection c, String sql, String arg) throws SQLException {
+        try (PreparedStatement ps = c.prepareStatement(sql)) {
+            ps.setString(1, arg);
+            try (ResultSet rs = ps.executeQuery()) {
+                return rs.next() ? rs.getString(1) : null;
+            }
+        }
+    }
+
+    public static List<String> columnNames(Connection c, String table) throws SQLException {
+        List<String> out = new ArrayList<>();
+        try (PreparedStatement ps = c.prepareStatement(
+                "SELECT column_name FROM information_schema.columns WHERE table_schema='public' AND table_name=? ORDER BY ordinal_position")) {
+            ps.setString(1, table);
+            try (ResultSet rs = ps.executeQuery()) {
+                while (rs.next()) {
+                    out.add(rs.getString(1));
+                }
+            }
+        }
+        return out;
+    }
+}