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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill pull request #666: DRILL-4956: Temporary tables support
Date Thu, 05 Jan 2017 02:34:21 GMT
Github user paul-rogers commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/sql/handlers/ViewHandler.java
    @@ -74,36 +93,49 @@ public PhysicalPlan getPlan(SqlNode sqlNode) throws ValidationException,
           final SchemaPlus defaultSchema = context.getNewDefaultSchema();
           final AbstractSchema drillSchema = SchemaUtilites.resolveToMutableDrillSchema(defaultSchema,
    -      final String schemaPath = drillSchema.getFullSchemaName();
           final View view = new View(newViewName, viewSql, newViewRelNode.getRowType(),
    -      final Table existingTable = SqlHandlerUtil.getTableFromSchema(drillSchema, newViewName);
    -      if (existingTable != null) {
    -        if (existingTable.getJdbcTableType() != Schema.TableType.VIEW) {
    -          // existing table is not a view
    -          throw UserException.validationError()
    -              .message("A non-view table with given name [%s] already exists in schema
    -                  newViewName, schemaPath)
    -              .build(logger);
    -        }
    -        if (existingTable.getJdbcTableType() == Schema.TableType.VIEW && !createView.getReplace())
    -          // existing table is a view and create view has no "REPLACE" clause
    -          throw UserException.validationError()
    -              .message("A view with given name [%s] already exists in schema [%s]",
    -                  newViewName, schemaPath)
    -              .build(logger);
    -        }
    -      }
    +      validateViewCreationPossibility(drillSchema, newViewName, createView.getReplace());
           final boolean replaced = drillSchema.createView(view);
           final String summary = String.format("View '%s' %s successfully in '%s' schema",
    -          createView.getName(), replaced ? "replaced" : "created", schemaPath);
    +          createView.getName(), replaced ? "replaced" : "created", drillSchema.getFullSchemaName());
           return DirectPlan.createDirectPlan(context, true, summary);
    +    /**
    +     * Validates if view can be created in indicated schema:
    +     * checks if object (persistent / temporary table) with the same exists
    +     * in indicated schema, or if view exists but replace flag is not set.
    +     *
    +     * @param drillSchema schema where views will be created
    +     * @param viewName view name
    +     * @param replaceView replace view if exists
    +     * @throws UserException if views can be created in indicated schema
    +     */
    +    private void validateViewCreationPossibility(AbstractSchema drillSchema, String viewName,
boolean replaceView) {
    +      final String schemaPath = drillSchema.getFullSchemaName();
    +      final Table existingTable = SqlHandlerUtil.getTableFromSchema(drillSchema, viewName);
    +      if ((existingTable != null && existingTable.getJdbcTableType() != Schema.TableType.VIEW)
    --- End diff --
    Yet another appearance of the temp table check...
    Given how often we do these checks, should we factor them out into functions?
    void assertTable(List<String> name, Boolean exists, Boolean isTemp)
    Where this one function checks if the thing is or is not a table, does or does not exist
(or doesn't care if exists is null), is or  is not a temp table (again with a doesn't care
    Having simpler functions makes code review easier and will certainly make changing the
code easier as the same logic does not have to be modified in many places.
    The form of the function is not important; feel free to improve it. It is the repetition
that we want to factor out.

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