Read Snowflake views definitions with the Snowflake-specific query (#…

…3794)

* Read Snowflake views definitions with the Snowflake-specific query

* Move view DDL reading to the GetViewDefinitionGeneratorSnowflake class; avoid NPE from a view definition in the ViewSnapshotGenerator

* Add logging for the case of empty view definition

* Add Javadoc to the GetViewDefinitionGeneratorSnowflake class

---------

Co-authored-by: filipe <flautert@liquibase.org>

liquibase-core/src/main/java/liquibase/snapshot/jvm/ViewSnapshotGenerator.java

@@ -83,18 +83,18 @@ protected DatabaseObject snapshotObject(DatabaseObject example, DatabaseSnapshot
                     database.setObjectQuotingStrategy(ObjectQuotingStrategy.QUOTE_ALL_OBJECTS);
                     String definition = database.getViewDefinition(schemaFromJdbcInfo, view.getName());
 
-                    if (definition.startsWith("FULL_DEFINITION: ")) {
+                    if (definition != null && definition.startsWith("FULL_DEFINITION: ")) {
                         definition = definition.replaceFirst("^FULL_DEFINITION: ", "");
                         view.setContainsFullDefinition(true);
                     }
 
                     // remove strange zero-termination seen on some Oracle view definitions
-                    int length = definition.length();
+                    int length = definition != null ? definition.length() : 0;
                     if (length > 0 && definition.charAt(length-1) == 0) {
                       definition = definition.substring(0, length-1);
                     }
 
-                    if (database instanceof InformixDatabase) {
+                    if (database instanceof InformixDatabase && definition != null) {
                         // Cleanup
                         definition = definition.trim();
                         definition = definition.replaceAll("\\s*,\\s*", ", ");

liquibase-snowflake/src/main/java/liquibase/database/core/SnowflakeDatabase.java

@@ -1,5 +1,6 @@
 package liquibase.database.core;
 
+import liquibase.CatalogAndSchema;
 import liquibase.Scope;
 import liquibase.database.AbstractJdbcDatabase;
 import liquibase.database.DatabaseConnection;
@@ -15,10 +16,12 @@
 import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.regex.Pattern;
 
 public class SnowflakeDatabase extends AbstractJdbcDatabase {
 
     public static final String PRODUCT_NAME = "Snowflake";
+    private static final Pattern CREATE_VIEW_AS_PATTERN = Pattern.compile("^CREATE\\s+.*?VIEW\\s+.*?AS\\s+", Pattern.CASE_INSENSITIVE | Pattern.DOTALL);
     private Set<String> systemTables = new HashSet<>();
     private Set<String> systemViews = new HashSet<>();
 
@@ -288,4 +291,18 @@ private Set<String> getDefaultReservedWords() {
 
         return reservedWords;
     }
+
+    public String getViewDefinition(CatalogAndSchema schema, String viewName) throws DatabaseException {
+        String definition = super.getViewDefinition(schema, viewName);
+        if (definition == null || definition.isEmpty()) {
+            Scope.getCurrentScope()
+                .getLog(getClass())
+                .info("Error reading '" + (viewName != null && viewName.isEmpty() ? viewName : "") + "' view definition");
+            return null;
+        }
+        if (definition.endsWith(";")) {
+            definition = definition.substring(0, definition.length() - 1);
+        }
+        return CREATE_VIEW_AS_PATTERN.matcher(definition).replaceFirst("");
+    }
 }

liquibase-snowflake/src/main/java/liquibase/sqlgenerator/core/GetViewDefinitionGeneratorSnowflake.java

@@ -0,0 +1,39 @@
+package liquibase.sqlgenerator.core;
+
+import liquibase.CatalogAndSchema;
+import liquibase.database.Database;
+import liquibase.database.core.SnowflakeDatabase;
+import liquibase.sql.Sql;
+import liquibase.sql.UnparsedSql;
+import liquibase.sqlgenerator.SqlGeneratorChain;
+import liquibase.statement.core.GetViewDefinitionStatement;
+
+/**
+ * Snowflake-specific view definition generator.
+ * Uses Snowflake-specific query to read full view definition statement from a database.
+ */
+public class GetViewDefinitionGeneratorSnowflake extends GetViewDefinitionGenerator {
+
+    @Override
+    public int getPriority() {
+        return PRIORITY_DATABASE;
+    }
+
+    @Override
+    public boolean supports(GetViewDefinitionStatement statement, Database database) {
+        return database instanceof SnowflakeDatabase;
+    }
+
+    @Override
+    public Sql[] generateSql(GetViewDefinitionStatement statement, Database database, SqlGeneratorChain sqlGeneratorChain) {
+        CatalogAndSchema schema = new CatalogAndSchema(statement.getCatalogName(), statement.getSchemaName()).customize(database);
+        // We can use non quoted schema/catalog/view names here.
+        // SELECT GET_DDL('VIEW', 'TEST.BAD$SCHEMA_NAME.BAD$%^VIEW_NAME', TRUE) - works fine.
+        // "TRUE" means that the returned result will be in the full representation
+        return new Sql[] {
+            new UnparsedSql( "SELECT GET_DDL('VIEW', '"
+                + schema.getCatalogName() + "." + schema.getSchemaName() + "." + statement.getViewName() + "', TRUE)"
+            )
+        };
+    }
+}

liquibase-snowflake/src/main/resources/META-INF/services/liquibase.sqlgenerator.SqlGenerator

@@ -5,4 +5,5 @@ liquibase.sqlgenerator.core.InsertOrUpdateGeneratorSnowflake
 liquibase.sqlgenerator.core.RenameTableGeneratorSnowflake
 liquibase.sqlgenerator.core.RenameViewGeneratorSnowflake
 liquibase.sqlgenerator.core.SetColumnRemarksGeneratorSnowflake
-liquibase.sqlgenerator.core.SetTableRemarksGeneratorSnowflake
+liquibase.sqlgenerator.core.SetTableRemarksGeneratorSnowflake
+liquibase.sqlgenerator.core.GetViewDefinitionGeneratorSnowflake