General Settings ================ logical_replication_mode ^^^^^^^^^^^^^^^^^^^^^^^^ Affects how the program interprets connections and table filter settings and also the requirements to check for in the connections before starting the comparison. Currently the possible values are: - ``off`` Assumes there’s no logical replication between the databases. - ``native`` Assumes there’s native logical replication between the databases. Enables the use of the ``Table Filter -> publications`` setting to specify the list of tables to use. Requires PostgreSQL 10+ on all databases. - ``pglogical`` Assumes there’s pglogical replication between the databases. Enables the use of the ``Table Filter -> replication_sets`` setting to specify the list of tables to use. Also enables the use of ``node_name`` to specify the data connections, which requires setting the ``Initial Connection`` that’s used to retrieve DSN information of the nodes. Requires the ``pglogical`` extensions to be installed on all databases. - ``bdr`` Assumes all data connections are nodes from the same PGD cluster. Enables use of the ``Table Filter -> replication_sets`` setting to specify the list of tables to use. Also enables the use of ``node_name`` to specify the data connections, which requires setting the ``Initial Connection`` that’s used to retrieve DSN information of the nodes. Requires ``pglogical`` and ``bdr`` extensions installed on all databases. all_bdr_nodes ^^^^^^^^^^^^^ If ``logical_replication_mode`` is set to ``bdr`` , then you can specify only the Initial Connection and let LiveCompare build the connection list based on the current list of active PGD nodes. Default: ``off`` . max_parallel_workers ^^^^^^^^^^^^^^^^^^^^ Number of parallel processes to consider. Each process works on a table from the queue. Default: ``2`` . .. Important:: Each process keeps N+1 open connections: one to each data connection and another one to the output database. buffer_size ^^^^^^^^^^^ Number of rows to retrieve from the tables on every data fetch operation. Default: ``4096`` . log_level ^^^^^^^^^ Verbosity level in the log file. Possible values: ``debug`` , ``info`` , ``warning`` , or ``error`` . Default: ``info`` . data_fetch_mode ^^^^^^^^^^^^^^^ Affects how LiveCompare fetches data from the database. - ``prepared_statements`` Uses prepared statements (a query with ``LIMIT`` ) for data fetch. Only a very small amount of data (``buffer_size = 4096`` rows by default) is fetched each time, so it has the smallest impact of all three modes, and for the same reason it’s the safer fetch mode. Allows asynchronous data fetch (defined by ``parallel_data_fetch`` ). For the general use case, this fetch method provides good performance, but a performance decrease can be felt for large tables. This is the default and strongly recommended when server load is medium-high. - ``server_side_cursors_with_hold`` Uses server-side cursors ``WITH HOLD`` for data fetch. As table data is retrieved in a single transaction, it holds back ``xmin`` and can cause bloat and replication issues and also prevent ``VACUUM`` from running well. Also, the ``WITH HOLD`` clause tells Postgres to materialize the query (workers can hang for a few seconds waiting for the data to materialize), so the whole table data consumes RAM and can be stored on Postgres side disk as temporary files. You can reduce all that impact by increasing ``buffer_size`` a little. Allows asynchronous data fetch (defined by ``parallel_data_fetch`` ). For the general use case, this fetch method doesn’t provide any benefits when compared to ``prepared_stataments`` , but for multiple small tables it’s faster. However, this mode is recommended only when load is very low, for example, on tests and migration scenarios. - ``server_side_cursors_without_hold`` Uses server-side cursors ``WITHOUT HOLD`` for data fetch. As ``server_side_cursors_with_hold`` , this mode can also hold back ``xmin`` , thus it potentially can cause bloat, ``VACUUM`` , and replication issues on Postgres. However, such impact is higher because ``WITHOUT HOLD`` cursors require an open transaction for the whole comparison session (this requirement will be lifted in later versions). As the snapshot is held for the whole comparison session, comparison results might be helpful depending on your use case. As the query isn’t materialized, memory usage and temp file generation remains low. Asynchronous data fetch isn’t allowed. In terms of performance, this mode is slower for the general use case, but for large tables it can be the faster. We recommend it when load on the database is low-medium. .. Important:: The choice of the right `data_fetch_mode` for the right scenario is very important. Using prepared statements has the smallest footprint on the database server, so it's the safest approach, and it's good for the general use case. Another point is that prepared statements allow LiveCompare to always see the latest version of the rows, which might not happen when using server-side cursors on a busy database. So we recommend using `prepared_statements` for production, high-load servers and either `server_side_cursors_*` setting for testing, migration scenarios, and low-load servers. The best strategy probably mixes `server_side_cursors_without_hold` for very large tables and `prepared_statements` for the remaining tables. The following table shows a comparison of the cost/benefit ratio. .. csv-table:: :header: "",prepared_statements,server_side_cursors_with_hold,server_side_cursors_without_hold :widths: 15,12,12,20 :align: left :class: longtable xmin hold,very low,medium,high xmin released per,buffer,chunk,whole comparison session temp files,very low,very high,low memory,very low,high,low allows async conns,yes,yes,no fastest for,general,small tables,large tables recommended load,high,very low,low-medium .. Note "Note about Oracle":: For Oracle, the `data_fetch_mode` setting is completely ignored, and data is always fetched from Oracle using a direct query. Data is taken in chunks of `buffer_size` through the client-side cursor. ~~\ ``parallel_chunk_rows`` ~~ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Removed in LiveCompare 3.0. If this setting is present in any ``.ini`` file, remove it before using the file with LiveCompare 3.0. parallel_data_fetch ^^^^^^^^^^^^^^^^^^^ Specifies whether data fetch is performed in parallel (that is, using async connections to the databases). Improves performance of multi-way comparison. If any data connections aren’t PostgreSQL, then this setting is automatically disabled. It’s allowed only when ``data_fetch_mode = prepared_statements`` or ``data_fetch_mode = server_side_cursors_with_hold`` . Default: ``on`` . ``comparison_algorithm`` : ^^^^^^^^^^^^^^^^^^^^^^^^^^ Affects how LiveCompare works through table rows to compare data. Using hashes is faster than full-row comparison. It can assume one of the following values: - ``full_row`` Disables row comparison using hashes. Full comparison, in this case, is performed by comparing the row column by column. For comparisons involving Oracle 10g database, ``full_row`` is the only valid value for the ``comparison_algorithm`` parameter. - ``row_hash`` Enables row comparison using hashes and enables table splitting. Tables are split so each worker compares a maximum of ``parallel_chunk_rows`` per table. Data row is hashed in PostgreSQL, so the comparison is faster than ``full_row`` . However, if the hash for a specific row doesn’t match, then for that specific row, LiveCompare falls back to the ``full_row`` algorithm (that is, compare row by row). If any data connection isn’t PostgreSQL, then LiveCompare uses a row hash that’s defined as the MD5 hash of the concatenated column values of the row being considered, a *common hash* among the database technologies being compared. - ``block_hash`` Works the same as ``row_hash`` , but instead of comparing row by row, LiveCompare builds a *block hash*, that is, a hash of the hashes of all rows in the data buffer that was just fetched (maximum of ``buffer_size`` rows). Conceptually it works like a two-level Merkle tree. If the block hash matches, then LiveCompare advances the whole block, which is why this comparison algorithm is faster than ``row_hash`` . If block hash doesn’t match, then LiveCompare falls back to ``row_hash`` and performs the comparison row by row in the buffer to find the divergent rows. This is the default value. min_time_between_heart_beats ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Time in seconds to wait before logging a *heart beat* message to the log. Each worker tracks it separately per round part being compared. Default: 30 seconds. min_time_between_round_saves ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Time in seconds to wait before updating each round state when the comparison algorithm is in progress. A round save can happen only during a heart beat, so ``min_time_between_round_saves`` must be greater than or equal to ``min_time_between_heart_beats`` . When the round finishes, LiveCompare always updates the round state for that table. Default: 60 seconds. .. Important:: If you cancel execution of LiveCompare by pressing **Ctrl-C** and start it again, then LiveCompare resumes the round for that table, starting from the point where the round state was saved. comparison_cost_limit ^^^^^^^^^^^^^^^^^^^^^ If > 0, corresponds to a number of rows each worker processes before taking a nap of ``comparison_cost_delay`` seconds. Defaults to 0, meaning that each worker processes rows without taking a nap. comparison_cost_delay ^^^^^^^^^^^^^^^^^^^^^ If ``comparison_cost_limit > 0`` , then this setting specifies how long each worker sleeps. Default: ``0.0`` . stop_after_time ^^^^^^^^^^^^^^^ Time in seconds after which LiveCompare stop as if you press **Ctrl-C**. You can resume the comparison session that was interrupted, if not finished yet, by passing the session ID as an argument in the command line. Default: ``stop_after_time = 0`` , which means that automatic interruption is disabled. consensus_mode ^^^^^^^^^^^^^^ Consensus algorithm used by LiveCompare to determine which data connections are divergent. Possible values are ``off`` , ``simple_majority`` , ``quorum_based`` , or ``source_of_truth`` . If ``consensus_mode = source_of_truth`` , then ``difference_sources_of_truth`` must be filled. Default: ``simple_majority`` . .. Note:: If `consensus_mode = off` and `comparison_algorithm = block_hash` , LiveCompare won't switch to a more granular comparison algorithm. This significantly improves the performance when divergences are found for a specific table, at the cost of not having the information about which rows are divergent. The user can subsequently run LiveCompare again adding the divergent tables, if any, to the `[Table Filter]` and compare only the divergent tables to get the information about which rows are divergent. difference_required_quorum ^^^^^^^^^^^^^^^^^^^^^^^^^^ If ``consensus_mode = quorum_based`` , then this setting specifies the minimum quorum required to decide which connections are divergent. Must be a number between 0.0 and 1.0. 0.0 means no connection is required, and 1.0 means all connections are required. Both cases are extreme and we don’t recommend using them. The default value is 0.5, and we recommend using a value close to that. difference_sources_of_truth ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Comma-separated list of connections names (or node names, if ``logical_replication_mode = bdr`` and ``all_bdr_nodes = on`` ) to consider as the source of truth. It’s used only when ``consensus_mode = source_of_truth`` . For example: ``difference_sources_of_truth = node1,node2`` . In this example, either the sections ``node1 Connection`` and ``node2 Connection`` must be defined in the ``.ini`` file or ``all_bdr_nodes = on`` and only the ``Initial Connection`` is defined, while ``node1`` and ``node2`` must be valid PGD node names. difference_tie_breakers ^^^^^^^^^^^^^^^^^^^^^^^ Comma-separated list of connection names (or node names, if ``logical_replication_mode = bdr`` and ``all_bdr_nodes = on`` ) to be considered as tie breakers whenever the consensus algorithm finds a tie situation. For example: ``difference_tie_breakers = node1,node2`` . In this example, either the sections ``node1 Connection`` and ``node2 Connections`` must be defined in the ``.ini`` file or ``all_bdr_nodes = on`` and only the ``Initial Connection`` is defined, while ``node1`` and ``node2`` must be valid PGD node names. Default: Don’t consider any connection as tie breaker. difference_statements ^^^^^^^^^^^^^^^^^^^^^ Controls the kind of DML statements for LiveCompare to generate. The value of ``difference_statements`` can be one of: - ``all`` (default) - ``inserts`` - ``updates`` - ``deletes`` - ``inserts_updates`` - ``inserts_deletes`` - ``updates_deletes`` difference_allow_null_updates ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Determines whether commands like ``UPDATE SET col = NULL`` are allowed in the difference report. Default: ``on`` . difference_statement_order ^^^^^^^^^^^^^^^^^^^^^^^^^^ Controls order of DML statements that LiveCompare generates. The value of ``difference_statement_order`` can be one of: - ``delete_insert_update`` - ``delete_update_insert`` (default) - ``insert_update_delete`` - ``insert_delete_update`` - ``update_insert_delete`` - ``update_delete_insert`` difference_fix_replication_origin ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ When working with PGD databases, for difference, LiveCompare creates a specific replication origin if it doesn’t exist yet. It then uses the replication origin to create an apply script with DML fixes. The setting ``difference_fix_replication_origin`` specifies the name of the replication origin used by LiveCompare. If you don’t set any value for this setting, then LiveCompare sets ``difference_fix_replication_origin = bdr_local_only_origin`` . The replication origin that LiveCompare creates isn’t dropped to allow verification after the comparison. However, if needed, you can manually drop the replication origin later. Requires ``logical_replication_mode = bdr`` . .. Important:: PGD 3.6.18 introduced the new pre-created `bdr_local_only_origin` replication origin to use for applying local-only transactions. So if LiveCompare is connected to PGD 3.6.18, it doesn't create this replication origin, and we recommend you don't try to drop this replication origin. difference_fix_start_query ^^^^^^^^^^^^^^^^^^^^^^^^^^ Arbitrary query that’s executed at the beginning of the apply script generated by LiveCompare. Additionally, if a PGD comparison is being performed and the ``difference_fix_start_query`` is empty, then LiveCompare also automatically does the following: - If the divergent connection is PGD 3.6.7, adds ``SET LOCAL bdr.xact_replication = off;`` - Adds commands that set up transaction to use the replication origin specified in ``difference_fix_replication_origin`` show_progress_bars ^^^^^^^^^^^^^^^^^^ Determines whether to show progress bars in the console output. Disabling this setting might be useful for batch executions. Default: ``on`` . output_schema ^^^^^^^^^^^^^ In the output connection, the schema where the comparison report tables are created. Default: ``livecompare`` . hash_column_name ^^^^^^^^^^^^^^^^ Every data fetch contains a specific column that’s the hash of all actual columns in the row. This setting specifies the name of this column. Default: ``livecompare_hash`` . rownumber_column_name ^^^^^^^^^^^^^^^^^^^^^ Some fetches need to use the ``row_number()`` function value inside a query column. This setting specifies the name of this column. Default: ``livecompare_rownumber`` . fetch_row_origin ^^^^^^^^^^^^^^^^ When this setting is enabled, LiveCompare fetches the origin name for each divergent row, which might be useful for debugging purposes. To be enabled, requires ``logical_replication_mode`` set to ``pglogical`` or ``bdr`` . Default: ``off`` . column_intersection ^^^^^^^^^^^^^^^^^^^ When this setting is enabled, for a given table that’s being compared, LiveCompare works only on the intersection of columns from the table on all connections, ignoring extra columns that might exist on any of the connections. When this setting is disabled, LiveCompare checks if columns are equivalent on the table on all connections and aborts the comparison of the table if there are any column mismatches. Default: ``off`` . .. Important:: If a table has PK, then the PK columns aren't allowed to be different, even if `column_intersection = on` . ignore_nullable ^^^^^^^^^^^^^^^ For a specific table comparison, if LiveCompare is using a comparison key different from the primary key, then LiveCompare requires all columns to be ``NOT NULL`` if ``ignore_nullable`` is enabled (default). You can override that behavior by setting ``ignore_nullable = off`` , which allows LiveCompare to consider null-able columns in the comparison, which in some corner cases can produce false positives. check_uniqueness_enforcement ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ If LiveCompare is using a user-defined comparison key or using all columns in the table as a comparison key, then LiveCompare checks for table uniqueness on the comparison key if setting ``check_uniqueness_enforcement`` is enabled (default). oracle_ignore_unsortable ^^^^^^^^^^^^^^^^^^^^^^^^ When enabled, tells LiveCompare to ignore columns with Oracle unsortable data types (BLOB, CLOB, NCLOB, BFILE) if column isn’t part of the table PK. If enabling this setting, we recommend also enabling ``column_intersection`` . oracle_user_tables_only ^^^^^^^^^^^^^^^^^^^^^^^ When enabled, tells LiveCompare to fetch table metadata only from the Oracle logged-in user. This approach is faster because it reads, for example, from ``sys.user_tables`` and ``sys.user_tab_columns`` instead of ``sys.all_tables`` and ``sys.all_tab_columns`` . Default: ``off`` . oracle_fetch_fk_metadata ^^^^^^^^^^^^^^^^^^^^^^^^ When enabled, tells LiveCompare to fetch foreign-key metadata, which can be a slow operation. Overrides the value of the setting ``fetch_fk_metadata`` on the Oracle connection. Default: ``off`` . schema_qualified_table_names ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Table names are treated as schema qualified when this setting is enabled. Disabling it allows comparing tables without using schema-qualified table names. On Oracle x Postgres comparisons, it requires also enabling ``oracle_user_tables_only`` . On Postgres x Postgres, it allows for comparisons of tables that are under different schemas, even in the same database. Also, when ``schema_qualified_table_names`` is enabled, ``Table Filter -> tables`` , ``Row Filter`` , and ``Column Filter`` allow table name without the schema name. Default: ``on`` . ~~\ ``force_collate`` ~~ ^^^^^^^^^^^^^^^^^^^^^^^^ Removed in LiveCompare 3.0. If this setting is present in any ``.ini`` file, remove it before using the file with LiveCompare 3.0. work_directory ^^^^^^^^^^^^^^ Path to the ``LiveCompare`` working directory. The session folder containing output files is created in this directory. Default: ``.`` (current directory). abort_on_setup_error ^^^^^^^^^^^^^^^^^^^^ When enabled, if LiveCompare encounters any error when trying to set up a table comparison round, the whole comparison session is aborted. Default: ``off`` . .. Important:: Setting `abort_on_setup_error` is considered only during `compare` mode. In `recheck` mode, LiveCompare always aborts at the first error in setup. custom_dollar_quoting_delimiter ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ When LiveCompare finds differences, it outputs the DML using dollar quoting on strings. The default behavior is to create a random string to compose it. If you want by any means to use a custom one, you can set this parameter as the delimiter to use. You need to set only the constant, not the ``$`` symbols around the constant. Default: ``off`` , which means LiveCompare uses an ``md5`` hash of the word ``LiveCompare`` . session_replication_role_replica ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ When enabled, LiveCompare uses the ``session_replication_role`` PostgreSQL setting as ``replica`` in the output apply scripts. That’s useful if you want to prevent firing triggers and rules while applying DML in the nodes with divergences. Enabling it requires a PostgreSQL superuser. Otherwise, it has no effect. Default: ``off`` . split_updates ^^^^^^^^^^^^^ When enabled, LiveCompare splits ``UPDATE`` divergences. That is, instead of generating an ``UPDATE`` DML, it generates corresponding ``DELETE`` and ``INSERT`` in the apply script. Default: ``off`` . float_point_round ^^^^^^^^^^^^^^^^^ An integer to specify decimal digits that LiveCompare rounds when comparing float-point values coming from the database Default: ``-1`` , which disables float-point rounding.