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209 lines
6.6 KiB
ReStructuredText
209 lines
6.6 KiB
ReStructuredText
Migrating a SQLite database to PostgreSQL
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=========================================
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This command instructs pgloader to load data from a SQLite file. Automatic
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discovery of the schema is supported, including build of the indexes.
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Here's an example::
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load database
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from sqlite:///Users/dim/Downloads/lastfm_tags.db
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into postgresql:///tags
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with include drop, create tables, create indexes, reset sequences
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set work_mem to '16MB', maintenance_work_mem to '512 MB';
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The `sqlite` command accepts the following clauses and options.
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SQLite Database Source Specification: FROM
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------------------------------------------
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Path or HTTP URL to a SQLite file, might be a `.zip` file.
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SQLite Database Migration Options: WITH
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---------------------------------------
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When loading from a `SQLite` database, the following options are
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supported:
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When loading from a `SQLite` database, the following options are
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supported, and the default *WITH* clause is: *no truncate*, *create
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tables*, *include drop*, *create indexes*, *reset sequences*, *downcase
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identifiers*, *encoding 'utf-8'*.
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- *include drop*
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When this option is listed, pgloader drops all the tables in the target
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PostgreSQL database whose names appear in the SQLite database. This
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option allows for using the same command several times in a row until
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you figure out all the options, starting automatically from a clean
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environment. Please note that `CASCADE` is used to ensure that tables
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are dropped even if there are foreign keys pointing to them. This is
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precisely what `include drop` is intended to do: drop all target tables
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and recreate them.
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Great care needs to be taken when using `include drop`, as it will
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cascade to *all* objects referencing the target tables, possibly
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including other tables that are not being loaded from the source DB.
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- *include no drop*
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When this option is listed, pgloader will not include any `DROP`
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statement when loading the data.
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- *truncate*
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When this option is listed, pgloader issue the `TRUNCATE` command
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against each PostgreSQL table just before loading data into it.
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- *no truncate*
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When this option is listed, pgloader issues no `TRUNCATE` command.
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- *disable triggers*
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When this option is listed, pgloader issues an `ALTER TABLE ... DISABLE
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TRIGGER ALL` command against the PostgreSQL target table before copying
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the data, then the command `ALTER TABLE ... ENABLE TRIGGER ALL` once the
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`COPY` is done.
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This option allows loading data into a pre-existing table ignoring
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the *foreign key constraints* and user defined triggers and may
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result in invalid *foreign key constraints* once the data is loaded.
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Use with care.
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- *create tables*
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When this option is listed, pgloader creates the table using the meta
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data found in the `SQLite` file, which must contain a list of fields
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with their data type. A standard data type conversion from SQLite to
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PostgreSQL is done.
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- *create no tables*
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When this option is listed, pgloader skips the creation of table before
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loading data, target tables must then already exist.
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Also, when using *create no tables* pgloader fetches the metadata
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from the current target database and checks type casting, then will
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remove constraints and indexes prior to loading the data and install
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them back again once the loading is done.
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- *create indexes*
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When this option is listed, pgloader gets the definitions of all the
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indexes found in the SQLite database and create the same set of index
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definitions against the PostgreSQL database.
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- *create no indexes*
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When this option is listed, pgloader skips the creating indexes.
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- *drop indexes*
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When this option is listed, pgloader drops the indexes in the target
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database before loading the data, and creates them again at the end
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of the data copy.
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- *reset sequences*
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When this option is listed, at the end of the data loading and after
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the indexes have all been created, pgloader resets all the
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PostgreSQL sequences created to the current maximum value of the
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column they are attached to.
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- *reset no sequences*
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When this option is listed, pgloader skips resetting sequences after the
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load.
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The options *schema only* and *data only* have no effects on this
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option.
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- *schema only*
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When this option is listed pgloader will refrain from migrating the data
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over. Note that the schema in this context includes the indexes when the
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option *create indexes* has been listed.
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- *data only*
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When this option is listed pgloader only issues the `COPY` statements,
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without doing any other processing.
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- *encoding*
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This option allows to control which encoding to parse the SQLite text
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data with. Defaults to UTF-8.
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SQLite Database Casting Rules
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-----------------------------
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The command *CAST* introduces user-defined casting rules.
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The cast clause allows to specify custom casting rules, either to overload
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the default casting rules or to amend them with special cases.
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SQlite Database Partial Migrations
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----------------------------------
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INCLUDING ONLY TABLE NAMES LIKE
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Introduce a comma separated list of table name patterns used to limit the
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tables to migrate to a sublist.
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Example::
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including only table names like 'Invoice%'
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EXCLUDING TABLE NAMES LIKE
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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Introduce a comma separated list of table name patterns used to exclude
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table names from the migration. This filter only applies to the result of
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the *INCLUDING* filter.
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::
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excluding table names like 'appointments'
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Default SQLite Casting Rules
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----------------------------
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When migrating from SQLite the following Casting Rules are provided:
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Numbers::
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type tinyint to smallint using integer-to-string
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type integer to bigint using integer-to-string
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type float to float using float-to-string
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type real to real using float-to-string
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type double to double precision using float-to-string
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type numeric to numeric using float-to-string
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type decimal to numeric using float-to-string
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Texts::
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type character to text drop typemod
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type varchar to text drop typemod
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type nvarchar to text drop typemod
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type char to text drop typemod
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type nchar to text drop typemod
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type nvarchar to text drop typemod
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type clob to text drop typemod
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Binary::
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type blob to bytea
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Date::
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type datetime to timestamptz using sqlite-timestamp-to-timestamp
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type timestamp to timestamptz using sqlite-timestamp-to-timestamp
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type timestamptz to timestamptz using sqlite-timestamp-to-timestamp
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