Add proj_context_get_database_structure() to dump structure of empty valid auxiliary DB

3 files changed, 125 insertions, 51 deletions

diff --git a/src/iso19111/c_api.cpp b/src/iso19111/c_api.cpp
index a79b387e..2a655e51 100644
--- a/src/iso19111/c_api.cpp
+++ b/src/iso19111/c_api.cpp
@@ -105,6 +105,28 @@ static void PROJ_NO_INLINE proj_log_debug(PJ_CONTEXT *ctx, const char *function,
 
 // ---------------------------------------------------------------------------
 
+template <class T> static PROJ_STRING_LIST to_string_list(T &&set) {
+    auto ret = new char *[set.size() + 1];
+    size_t i = 0;
+    for (const auto &str : set) {
+        try {
+            ret[i] = new char[str.size() + 1];
+        } catch (const std::exception &) {
+            while (--i > 0) {
+                delete[] ret[i];
+            }
+            delete[] ret;
+            throw;
+        }
+        std::memcpy(ret[i], str.c_str(), str.size() + 1);
+        i++;
+    }
+    ret[i] = nullptr;
+    return ret;
+}
+
+// ---------------------------------------------------------------------------
+
 void proj_context_delete_cpp_context(struct projCppContext *cppContext) {
     delete cppContext;
 }
@@ -390,6 +412,35 @@ const char *proj_context_get_database_metadata(PJ_CONTEXT *ctx,
 
 // ---------------------------------------------------------------------------
 
+/** \brief Return the database structure
+ *
+ * Return SQL statements to run to initiate a new valid auxiliary empty
+ * database. It contains definitions of tables, views and triggers, as well
+ * as metadata for the version of the layout of the database.
+ *
+ * @param ctx PROJ context, or NULL for default context
+ * @param options null-terminated list of options, or NULL. None currently.
+ * @return list of SQL statements (to be freed with proj_string_list_destroy()),
+ *         or NULL in case of error.
+ * @since 8.1
+ */
+PROJ_STRING_LIST
+proj_context_get_database_structure(PJ_CONTEXT *ctx,
+                                    const char *const *options) {
+    SANITIZE_CTX(ctx);
+    (void)options;
+    try {
+        auto ret = to_string_list(getDBcontext(ctx)->getDatabaseStructure());
+        ctx->safeAutoCloseDbIfNeeded();
+        return ret;
+    } catch (const std::exception &e) {
+        proj_log_error(ctx, __FUNCTION__, e.what());
+        return nullptr;
+    }
+}
+
+// ---------------------------------------------------------------------------
+
 /** \brief Guess the "dialect" of the WKT string.
  *
  * @param ctx PROJ context, or NULL for default context
@@ -508,28 +559,6 @@ PJ *proj_create(PJ_CONTEXT *ctx, const char *text) {
 
 // ---------------------------------------------------------------------------
 
-template <class T> static PROJ_STRING_LIST to_string_list(T &&set) {
-    auto ret = new char *[set.size() + 1];
-    size_t i = 0;
-    for (const auto &str : set) {
-        try {
-            ret[i] = new char[str.size() + 1];
-        } catch (const std::exception &) {
-            while (--i > 0) {
-                delete[] ret[i];
-            }
-            delete[] ret;
-            throw;
-        }
-        std::memcpy(ret[i], str.c_str(), str.size() + 1);
-        i++;
-    }
-    ret[i] = nullptr;
-    return ret;
-}
-
-// ---------------------------------------------------------------------------
-
 /** \brief Instantiate an object from a WKT string.
  *
  * This function calls osgeo::proj::io::WKTParser::createFromWKT()
diff --git a/src/iso19111/factory.cpp b/src/iso19111/factory.cpp
index 750e9054..af9736e6 100644
--- a/src/iso19111/factory.cpp
+++ b/src/iso19111/factory.cpp
@@ -274,6 +274,8 @@ struct DatabaseContext::Private {
     std::vector<std::string> auxiliaryDatabasePaths_{};
     bool close_handle_ = true;
     sqlite3 *sqlite_handle_{};
+    int nLayoutVersionMajor_ = 0;
+    int nLayoutVersionMinor_ = 0;
     std::map<std::string, sqlite3_stmt *> mapSqlToStatement_{};
     PJ_CONTEXT *pjCtxt_ = nullptr;
     int recLevel_ = 0;
@@ -305,7 +307,8 @@ struct DatabaseContext::Private {
     lru11::Cache<std::string, std::list<std::string>> cacheAliasNames_{
         CACHE_SIZE};
 
-    void checkDatabaseLayout();
+    void checkDatabaseLayout(const std::string &path,
+                             const std::string &dbNamePrefix);
 
     static void insertIntoCache(LRUCacheOfObjects &cache,
                                 const std::string &code,
@@ -709,10 +712,22 @@ void DatabaseContext::Private::open(const std::string &databasePath,
 
 // ---------------------------------------------------------------------------
 
-void DatabaseContext::Private::checkDatabaseLayout() {
-    auto res = run("SELECT key, value FROM metadata WHERE key IN "
+void DatabaseContext::Private::checkDatabaseLayout(
+    const std::string &path, const std::string &dbNamePrefix) {
+    if (!dbNamePrefix.empty() && run("SELECT 1 FROM " + dbNamePrefix +
+                                     "sqlite_master WHERE name = 'metadata'")
+                                     .empty()) {
+        // Accept auxiliary databases without metadata table (sparse DBs)
+        return;
+    }
+    auto res = run("SELECT key, value FROM " + dbNamePrefix +
+                   "metadata WHERE key IN "
                    "('DATABASE.LAYOUT.VERSION.MAJOR', "
                    "'DATABASE.LAYOUT.VERSION.MINOR')");
+    if (res.empty() && !dbNamePrefix.empty()) {
+        // Accept auxiliary databases without layout metadata.
+        return;
+    }
     if (res.size() != 2) {
         // The database layout of PROJ 7.2 that shipped with EPSG v10.003 is
         // at the time of writing still compatible of the one we support.
@@ -730,36 +745,47 @@ void DatabaseContext::Private::checkDatabaseLayout() {
         }
 
         throw FactoryException(
-            databasePath_ +
-            " lacks DATABASE.LAYOUT.VERSION.MAJOR / "
-            "DATABASE.LAYOUT.VERSION.MINOR "
-            "metadata. It comes from another PROJ installation.");
+            path + " lacks DATABASE.LAYOUT.VERSION.MAJOR / "
+                   "DATABASE.LAYOUT.VERSION.MINOR "
+                   "metadata. It comes from another PROJ installation.");
     }
-    int nMajor = 0;
-    int nMinor = 0;
+    int major = 0;
+    int minor = 0;
     for (const auto &row : res) {
         if (row[0] == "DATABASE.LAYOUT.VERSION.MAJOR") {
-            nMajor = atoi(row[1].c_str());
+            major = atoi(row[1].c_str());
         } else if (row[0] == "DATABASE.LAYOUT.VERSION.MINOR") {
-            nMinor = atoi(row[1].c_str());
+            minor = atoi(row[1].c_str());
         }
     }
-    if (nMajor != DATABASE_LAYOUT_VERSION_MAJOR) {
+    if (major != DATABASE_LAYOUT_VERSION_MAJOR) {
         throw FactoryException(
-            databasePath_ +
-            " contains DATABASE.LAYOUT.VERSION.MAJOR = " + toString(nMajor) +
+            path +
+            " contains DATABASE.LAYOUT.VERSION.MAJOR = " + toString(major) +
             " whereas " + toString(DATABASE_LAYOUT_VERSION_MAJOR) +
             " is expected. "
             "It comes from another PROJ installation.");
     }
-    if (nMinor < DATABASE_LAYOUT_VERSION_MINOR) {
+    if (minor < DATABASE_LAYOUT_VERSION_MINOR) {
         throw FactoryException(
-            databasePath_ +
-            " contains DATABASE.LAYOUT.VERSION.MINOR = " + toString(nMinor) +
+            path +
+            " contains DATABASE.LAYOUT.VERSION.MINOR = " + toString(minor) +
             " whereas a number >= " + toString(DATABASE_LAYOUT_VERSION_MINOR) +
             " is expected. "
             "It comes from another PROJ installation.");
     }
+    if (dbNamePrefix.empty()) {
+        nLayoutVersionMajor_ = major;
+        nLayoutVersionMinor_ = minor;
+    } else if (nLayoutVersionMajor_ != major || nLayoutVersionMinor_ != minor) {
+        throw FactoryException(
+            "Auxiliary database " + path +
+            " contains a DATABASE.LAYOUT.VERSION =  " + toString(major) + '.' +
+            toString(minor) +
+            " which is different from the one from the main database " +
+            databasePath_ + " which is " + toString(nLayoutVersionMajor_) +
+            '.' + toString(nLayoutVersionMinor_));
+    }
 }
 
 // ---------------------------------------------------------------------------
@@ -777,17 +803,28 @@ void DatabaseContext::Private::setHandle(sqlite3 *sqlite_handle) {
 // ---------------------------------------------------------------------------
 
 std::vector<std::string> DatabaseContext::Private::getDatabaseStructure() {
-    const char *sqls[] = {
-        "SELECT sql FROM sqlite_master WHERE type = 'table'",
-        "SELECT sql FROM sqlite_master WHERE type = 'view'",
-        "SELECT sql FROM sqlite_master WHERE type = 'trigger'"};
+    const std::string dbNamePrefix(auxiliaryDatabasePaths_.empty() &&
+                                           memoryDbForInsertPath_.empty()
+                                       ? ""
+                                       : "db_0.");
+    const auto sqlBegin("SELECT sql||';' FROM " + dbNamePrefix +
+                        "sqlite_master WHERE type = ");
+    const char *const objectTypes[] = {"'table'", "'view'", "'trigger'"};
     std::vector<std::string> res;
-    for (const auto &sql : sqls) {
-        auto sqlRes = run(sql);
+    for (const auto &objectType : objectTypes) {
+        const auto sqlRes = run(sqlBegin + objectType);
         for (const auto &row : sqlRes) {
             res.emplace_back(row[0]);
         }
     }
+    if (nLayoutVersionMajor_ > 0) {
+        res.emplace_back(
+            "INSERT INTO metadata VALUES('DATABASE.LAYOUT.VERSION.MAJOR'," +
+            toString(nLayoutVersionMajor_) + ");");
+        res.emplace_back(
+            "INSERT INTO metadata VALUES('DATABASE.LAYOUT.VERSION.MINOR'," +
+            toString(nLayoutVersionMinor_) + ");");
+    }
     return res;
 }
 
@@ -828,13 +865,16 @@ void DatabaseContext::Private::attachExtraDatabases(
         "' AS db_0");
     detach_ = true;
     int count = 1;
-    for (const auto &otherDb : auxiliaryDatabasePaths) {
+    for (const auto &otherDbPath : auxiliaryDatabasePaths) {
+        const auto attachedDbName("db_" + toString(static_cast<int>(count)));
         std::string sql = "ATTACH DATABASE '";
-        sql += replaceAll(otherDb, "'", "''");
-        sql += "' AS db_";
-        sql += toString(static_cast<int>(count));
+        sql += replaceAll(otherDbPath, "'", "''");
+        sql += "' AS ";
+        sql += attachedDbName;
         count++;
         run(sql);
+
+        checkDatabaseLayout(otherDbPath, attachedDbName + '.');
     }
 
     for (const auto &pair : tableStructure) {
@@ -2452,11 +2492,11 @@ DatabaseContext::create(const std::string &databasePath,
     auto dbCtx = DatabaseContext::nn_make_shared<DatabaseContext>();
     auto dbCtxPrivate = dbCtx->getPrivate();
     dbCtxPrivate->open(databasePath, ctx);
+    dbCtxPrivate->checkDatabaseLayout(databasePath, std::string());
     if (!auxiliaryDatabasePaths.empty()) {
         dbCtxPrivate->attachExtraDatabases(auxiliaryDatabasePaths);
         dbCtxPrivate->auxiliaryDatabasePaths_ = auxiliaryDatabasePaths;
     }
-    dbCtxPrivate->checkDatabaseLayout();
     dbCtxPrivate->self_ = dbCtx.as_nullable();
     return dbCtx;
 }
@@ -2527,6 +2567,9 @@ void DatabaseContext::startInsertStatementsSession() {
             "stopInsertStatementsSession() is.");
     }
 
+    d->memoryDbForInsertPath_.clear();
+    const auto sqlStatements = getDatabaseStructure();
+
     // Create a in-memory temporary sqlite3 database
     std::ostringstream buffer;
     buffer << "file:temp_db_for_insert_statements_";
@@ -2541,7 +2584,6 @@ void DatabaseContext::startInsertStatementsSession() {
     }
 
     // Fill the structure of this database
-    const auto sqlStatements = getDatabaseStructure();
     for (const auto &sql : sqlStatements) {
         if (sqlite3_exec(d->memoryDbHandle_, sql.c_str(), nullptr, nullptr,
                          nullptr) != SQLITE_OK) {
diff --git a/src/proj.h b/src/proj.h
index 83975123..63821489 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -1044,6 +1044,9 @@ const char PROJ_DLL *proj_context_get_database_path(PJ_CONTEXT *ctx);
 const char PROJ_DLL *proj_context_get_database_metadata(PJ_CONTEXT* ctx,
                                                         const char* key);
 
+PROJ_STRING_LIST PROJ_DLL proj_context_get_database_structure(
+                                                PJ_CONTEXT* ctx,
+                                                const char* const *options);
 
 PJ_GUESSED_WKT_DIALECT PROJ_DLL proj_context_guess_wkt_dialect(PJ_CONTEXT *ctx,
                                                                const char *wkt);