mirror of https://github.com/citusdata/citus.git
65bd540943
DESCRIPTION: Add GUC to control ddl creation behaviour in transactions Historically we would _not_ propagate objects when we are in a transaction block. Creation of distributed tables would not always work in sequential mode, hence objects created in the same transaction as distributing a table that would use the just created object wouldn't work. The benefit was that the user could still benefit from parallelism. Now that the creation of distributed tables is supported in sequential mode it would make sense for users to force transactional consistency of ddl commands for distributed tables. A transaction could switch more aggressively to sequential mode when creating new objects in a transaction. We don't change the default behaviour just yet. Also, many objects would not even propagate their creation when the transaction was already set to sequential, leaving the probability of a self deadlock. The new policy checks solve this discrepancy between objects as well. |
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|---|---|---|
| .. | ||
| README.md | ||
| alter_table.c | ||
| call.c | ||
| cascade_table_operation_for_connected_relations.c | ||
| citus_add_local_table_to_metadata.c | ||
| citus_global_signal.c | ||
| cluster.c | ||
| collation.c | ||
| create_distributed_table.c | ||
| database.c | ||
| dependencies.c | ||
| distribute_object_ops.c | ||
| drop_distributed_table.c | ||
| extension.c | ||
| foreign_constraint.c | ||
| foreign_server.c | ||
| function.c | ||
| grant.c | ||
| index.c | ||
| index_pg_source.c | ||
| local_multi_copy.c | ||
| multi_copy.c | ||
| policy.c | ||
| rename.c | ||
| role.c | ||
| schema.c | ||
| sequence.c | ||
| statistics.c | ||
| subscription.c | ||
| table.c | ||
| text_search.c | ||
| transmit.c | ||
| trigger.c | ||
| truncate.c | ||
| type.c | ||
| utility_hook.c | ||
| vacuum.c | ||
| variableset.c | ||
README.md
Commands
The commands module is modeled after backend/commands from the postgres repository and
contains the logic for Citus on how to run these commands on distributed objects. Even
though the structure of the directory has some resemblence to its postgres relative, files
here are somewhat more fine-grained. This is due to the nature of citus commands that are
heavily focused on distributed tables. Instead of having all commands in tablecmds.c
they are often moved to files that are named after the command.
| File | Description |
|---|---|
create_distributed_table.c |
Implementation of UDF's for creating distributed tables |
drop_distributed_table.c |
Implementation for dropping metadata for partitions of distributed tables |
extension.c |
Implementation of CREATE EXTENSION commands for citus specific checks |
foreign_constraint.c |
Implementation of helper functions for foreign key constraints |
grant.c |
Placeholder for code granting users access to relations, implemented as enterprise feature |
index.c |
Implementation of commands specific to indices on distributed tables |
multi_copy.c |
Implementation of COPY command. There are multiple different copy modes which are described in detail below |
policy.c |
Implementation of CREATE\ALTER POLICY commands. |
rename.c |
Implementation of ALTER ... RENAME ... commands. It implements the renaming of applicable objects, otherwise provides the user with a warning |
schema.c |
|
sequence.c |
Implementation of CREATE/ALTER SEQUENCE commands. Primarily checks correctness of sequence statements as they are not propagated to the worker nodes |
table.c |
|
transmit.c |
Implementation of COPY commands with format transmit set in the options. This format is used to transfer files from one node to another node |
truncate.c |
Implementation of TRUNCATE commands on distributed tables |
utility_hook.c |
This is the entry point from postgres into the commands module of citus. It contains the implementation that gets registered in postgres' ProcessUtility_hook callback to extends the functionality of the original ProcessUtility. This code is used to route the incoming commands to their respective implementation in Citus |
vacuum.c |
Implementation of VACUUM commands on distributed tables |
COPY
The copy command is overloaded for a couple of use-cases specific to citus. The syntax of the command stays the same, however the implementation might slightly differ from the stock implementation. The overloading is mostly done via extra options that Citus uses to indicate how to operate the copy. The options used are described below.
FORMAT transmit
Implemented in transmit.c
TODO: to be written by someone with enough knowledge to write how, when and why it is used.
FORMAT result
Implemented in multi_copy.c
TODO: to be written by someone with enough knowledge to write how, when and why it is used.