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Oracle to PostgreSQL migration guide

Convert an Oracle export from SQL Developer or SQLcl into a PostgreSQL script with the same tables, keys, indexes and data, and every rule the converter applies.

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IntoSQL reads the .sql file SQL Developer's Database Export or SQLcl writes, with DBMS_METADATA's table definitions and Insert into statements, and turns it into one PostgreSQL script with the same tables, columns, keys, indexes, foreign keys, defaults, counters and rows. It evaluates what those exports write for values: to_date and to_timestamp with their format, TO_CLOB and HEXTORAW pieces, decimal commas from German or Spanish sessions. Every value PostgreSQL can't hold as it is, and every object it doesn't carry, is listed in the report. The script loads on PostgreSQL 13 and later.

Convert in the browser: Oracle to PostgreSQL opens the converter set up for this pair.

Export for the best result

In SQL Developer, choose Tools, Database Export, with DDL and the Insert data format, as one file. SQLcl writes the same data with SET SQLFORMAT INSERT. Before exporting, set a date format that keeps the time and the century:

SQL
ALTER SESSION SET NLS_DATE_FORMAT = 'SYYYY-MM-DD HH24:MI:SS';
ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'SYYYY-MM-DD HH24:MI:SS.FF9';
  • The default format, DD-MON-RR, writes each date without its time and with two digits of the year; the report says so (oracle_date_format) and each date is read as its day, between 1950 and 2049.
  • A .dmp file from exp or expdp is binary. Import it into an Oracle database, Oracle Database Free runs in Docker, and export it with SQL Developer; the converter says so when it gets one (dump_oracle_binary).
  • Every test export comes from Oracle 21c and 23ai, in American, German and ISO sessions, and is compared with its source cell by cell.

Convert

In the browser, open Oracle to PostgreSQL or the converter on the home page, drop the export and choose PostgreSQL. It reads the file from your disk in pieces, twice, and writes the script as it goes, so the file is never uploaded and its size isn't limited by memory. The desktop app does the same with the file on disk.

With the command line:

Terminal
intosql inspect shop.sql
intosql convert shop.sql --to postgresql --output shop.postgresql.sql --report shop.report.json

inspect lists the tables, their rows and what won't be converted, without writing anything. convert writes the script and, with --report, the report as JSON.

Through the API, an export converts like any other file: open a conversion with its name and "output": {"dialect": "postgresql"}.

Load into PostgreSQL

Terminal
createdb shop
psql -v ON_ERROR_STOP=1 -d shop -f shop.postgresql.sql

The script creates the tables without keys, copies the rows with COPY, then adds keys, indexes, foreign keys and identities, so it loads fast and stops at the first error. Names Oracle stores in upper case become lower case (CUSTOMERS is customers), and quoted mixed-case names keep their case. NUMBER becomes numeric, or bigint when every value is a whole number, DATE becomes timestamp(0) so it keeps its time, and BINARY_DOUBLE keeps NaN and Infinity. Identity columns, and columns a trigger fills from a sequence, continue after the highest id; sequences continue from where the export says they reached.

Or load it straight in

intosql load and the desktop app load the dump into PostgreSQL without a script, with the same tables, keys and indexes the script creates:

Terminal
intosql load shop.sql --into postgres://ana@localhost/shop

It stops before writing anything when one of the dump's tables already exists. It loads in one transaction, so a failed load leaves nothing. Loading into a database server is part of IntoSQL Pro, with a 14-day trial. See Loading.

What isn't converted

Views, packages, procedures, functions, triggers other than one that fills a column from a sequence, types and synonyms are written in PL/SQL. They are listed in the report by kind and name, never dropped silently, so you can recreate them in PostgreSQL.

Data types

Oracle to PostgreSQL data types lists each type that changes in the script: what it becomes, why, and the report line.

Every other rule

Generated from the engine, where each rule is decided.

In Oracle In PostgreSQL Why Report line
collations that ignore case (BINARY_CI) exact comparison PostgreSQL compares text exactly, so columns that ignored case in Oracle now tell Ana and ana apart. case_insensitive_collation
CREATE SEQUENCE CREATE SEQUENCE with the same options The export writes where a sequence has reached as its START WITH, so it continues from there. None
virtual columns (GENERATED ALWAYS AS ... VIRTUAL) generated columns, STORED PostgreSQL 13 to 17 only store generated columns; the formula is the same, with || written so NULL counts as empty as in Oracle. virtual_as_stored
virtual columns with functions IntoSQL doesn't write, and the || operator a plain column A formula that can't be written for PostgreSQL leaves a plain column and a report line; the values the export wrote for virtual columns are left out, and PostgreSQL has none to compute. generated_not_translated
defaults with functions IntoSQL doesn't write (SYS_GUID(), ||) no default A default that can't be written for PostgreSQL is left out and reported. default_not_translated
CHECK constraints translated The same checks, tested as each row loads. None
CHECK constraints with functions IntoSQL doesn't write not created A check that can't be written for PostgreSQL is left out and reported. check_skipped
CHECK constraints that are DISABLE or ENABLE NOVALIDATE not created Oracle doesn't apply these checks to the rows already there, so the rows may break them. check_not_enforced
function-based, bitmap and domain indexes not created IntoSQL writes b-tree indexes on columns; create the others again after loading. index_skipped
foreign keys foreign keys, after the rows The rows load in any order, and the keys check them afterwards. None
foreign keys to tables the export doesn't create, and DISABLE or NOVALIDATE ones not created A key can't name a table that isn't there, and one Oracle doesn't check may have rows without a parent. foreign_key_skipped
partitioned tables one table with every partition's rows The rows are the same; partition the table again in PostgreSQL if it needs it. partitions_dropped
NOT NULL columns with values that become NULL NOT NULL dropped A column whose values had to become NULL can't keep NOT NULL, or the load would stop. not_null_relaxed
views, synonyms, types, packages, procedures, functions and other triggers listed in the report Their code is written in PL/SQL, so they are listed for you to recreate. not_converted_objects
exports without CREATE TABLE (data only) types read from the values A data-only export has only rows, so the types come from the values. no_schema
expressions in INSERT values other than the ones exports write NULL A converter that doesn't run a database can't evaluate them; to_date, to_timestamp, TO_CLOB, HEXTORAW and the others exports write are read. expression_value
text decoded twice (ñ) copied as it is The script holds exactly these characters, so they are copied; the report points them out. mojibake_suspected