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PostgreSQL Languages AST and statements prettifier

Project description


Lele Gaifax


GNU General Public License version 3 or later

Build status Documentation status Test coverage status

This is a Python 3 module that exposes the parse tree of a PostgreSQL statement (extracted by the almost standard PG parser repackaged as a standalone static library by libpg_query) as set of interconnected nodes, usually called an abstract syntax tree.

See a more detailed introduction in the documentation.


As usual, the easiest way is with pip:

$ pip install pglast

Alternatively you can clone the repository:

$ git clone --recursive

and install from there:

$ pip install ./pglast


There is a set of makefiles implementing the most common operations, a make help will show a brief table of contents. A comprehensive test suite, based on pytest, covers nearly 99% of the source lines.


Latest documentation is hosted by Read the Docs at


Version 6

6.2 (2024-02-01)

  • Almost no-op release to fix issue 144, producing correct wheels for macOS arm64

6.1 (2024-01-22)

6.0 (2024-01-22)

  • Produce wheels for macOS arm64

6.0.dev2 (2024-01-21)

  • Enable compilation on Windows and produce related 32bit and 64bit wheels (issue #7)

6.0.dev1 (2024-01-11)

  • Re-enable Linux 32bit wheels, thanks to libpg_query to 16-5.1.0

6.0.dev0 (2023-12-29)

  • No visible changes with respect to v5, apart from the support for new/revised syntaxes of PostgreSQL 16

  • Do not build binary wheels for Python 3.8

  • Skip compilation on Linux 32bit (see this comment for details)

Breaking changes
  • Target PostgreSQL 16, thanks to libpg_query 16-5.0.0

Version 5

5.9 (2024-01-22)

  • Fix issue 143, affecting AlterOwnerStmt and RenameStmt printers

5.8 (2024-01-11)

  • Fix issue #142, a glitch that affected 32-bit systems

5.7 (2023-12-23)

5.6 (2023-12-07)

  • Fix issue #138, a defect that hindered the creation of AST nodes that act as markers, (currently A_Star and CheckPointStmt), that do not carry any other information

  • Use Cython 3.0.6

  • Handle the ENABLE TRIGGER ALL in AlterTableCmd

  • Fix issue #136, a regression introduced by “Avoid overly abundancy of parentheses in expressions”

5.5 (2023-10-07)

  • Use Cython 3.0.3

  • Produce wheels using final Python 3.12 release, thanks to cibuildwheel 2.16.2

5.4 (2023-08-24)

  • Improve documentation, adding parser.Displacements, parser.scan and parser.split examples (issue #128)

  • Fix issues #129 and #130 (merged from version 4.4)

5.3 (2023-08-05)

5.2 (2023-05-20)

5.1 (2023-02-28)

5.0 (2023-02-19)

  • No changes

5.0.dev1 (2023-02-11)

Breaking changes
  • Change the type of the ast.Float value from Decimal to str

    Using a Decimal implies potential differences in the representation of floating numbers, and already caused issues (#91 and #100) in the past, making it impossible to render, say, SELECT 0.0e1, due to the fact that Decimal('0.0e1') resolves to Decimal('0').

5.0.dev0 (2022-12-19)

  • No visible changes with respect to v4, apart from the support for new/revised syntaxes of PostgreSQL 15

Breaking changes
  • Target PostgreSQL 15, thanks to libpg_query 15-4.0.0

Version 4

4.5 (unreleased)

4.4 (2023-08-24)

4.3 (2023-04-27)

4.2 (2023-02-27)

  • Handle special syntax required by SET TIME ZONE INTERVAL '-08:00' hour to minute

  • Fix mistype mapping of raw C “long” and “double” attributes, that were decorated with the wrong Python type

4.1 (2022-12-19)

  • Fix serialization glitches introduced by “Avoid overly abundancy of parentheses in expressions” (to be precise, by this commit)

4.0 (2022-12-12)

4.0.dev0 (2022-11-24)

  • Update libpg_query to 14-3.0.0

  • Avoid overly abundancy of parentheses in expressions


Breaking changes
  • Target PostgreSQL 14

  • The wrapper classes used in previous versions, implemented in pglast.node, are gone: now everything works on top of the AST classes (issue #80)

  • The Ancestor class is not iterable anymore: it was an internal implementation facility, now moved to a _iter_members() method

Version 3

3.18 (2023-08-24)

  • Fix BooleanTest printer, enclosing expression within parens in more cases (issue #129)

  • Fix Constraint printer, avoiding repetition of “DEFERRABLE INITIALLY DEFERRED” on some kind of constraints (issue #130)

3.17 (2022-11-04)

  • Fix AlterSubscriptionStmt printer, handling “SET PUBLICATION” without options

3.16 (2022-11-03)

3.15 (2022-10-17)

  • Produce Python 3.11 wheels (PR #108), thanks to cibuildwheel 2.11.1 and to Bastien Gandouet

3.14 (2022-08-08)

  • Harden the way Visitor handle modifications to the AST (issue #107)

3.13 (2022-06-29)

3.12 (2022-06-19)

  • Rewrite the implementation of the referenced_relations() function, that was flawed with regard to CTEs handling (issue #106), thanks to Michal Charemza for providing his own version

  • Improve WithClause printer indentation

  • Fix minor whitespace related issues in a few printer functions

3.11 (2022-05-29)

  • Fix the Visitor class, it was ignoring nodes nested in sub-lists

  • Reduce the size of the generated parser by factoring out common code into helper functions

3.10 (2022-05-11)

3.9 (2022-02-24)

  • Fix bug handling node containing a location field, e.g. CreateTableSpaceStmt (issue #98)

  • Properly handle dereferenced array expression (issue #99)

  • Avoid improper “floatification” of literal integers (issue #100)

3.8 (2021-12-28)

  • Fix glitch in the AST extractor tool (issue #97)

  • Add Linux AArch64 wheel build support (PR #95), thanks to odidev

  • Fix type mismatch when using --remove-pg_catalog-from-functions (PR #93), thanks to Boris Zentner

3.7 (2021-10-13)

3.6 (2021-10-09)

  • Use latest libpg_query, to fix an error parsing PLpgSQL statements (issue #88)

3.5 (2021-09-26)

  • Forward the special_functions option to substream, when concatenating items (issue #89)

  • Fix representation of floating point numbers without decimal digits (issue #91)

  • Produce Python 3.10 wheels, thanks to cibuildwheel 2.1.2

  • Update libpg_query to 13-2.0.7

  • New option --remove-pg_catalog-from-functions on the command line tool (PR #90), thanks to Boris Zentner

  • Implement more special functions (PR #92), thanks to Boris Zentner

3.4 (2021-08-21)

  • Fix another packaging issue, that prevented recompilation from the sdist .tar.gz (issue #86), thanks to Christopher Brichford

3.3 (2021-07-04)

3.2 (2021-06-25)

  • Effectively include libpg_query’s vendored sources (issue #82)

3.1 (2021-06-25)

  • Fix packaging glitch (issue #82)

  • Build wheels also for macOS

  • Update libpg_query to 13-2.0.5

3.0 (2021-06-04)

  • Fix glitch in the RawStream, avoiding spurious space after an open parenthesis

  • Improve the Visitor class, to make it easier altering the original tree

  • Properly handle nested lists in the serialization of AST Node

3.0.dev2 (2021-05-22)

  • Fix bug in CreateStmt printer (issue #79)

  • Make it possible to pass also concrete ast.Nodes to RawStream`

Breaking changes
  • To reduce confusion, the printer module has been removed: print-specific stuff is now directly exposed by the printers subpackage while serialization classes are now in the new stream module

  • The default value for the safety_belt option of the printify() function is now False

3.0.dev1 (2021-05-16)

  • Fix AT_SetIdentity, AT_EnableReplicaTrig and AlterSubscriptionStmt printers

  • Improve AlterTSConfigType and IntoClause printers

  • New generic “visitor pattern” (issue #51) exemplified by a new referenced_relations() function (issue #66)

  • Refine printing of SQL comments

  • Implement AlterExtensionStmt printer

3.0.dev0 (2021-05-03)

  • Expose the new pg_query_scan() function as parser.scan()

  • Expose the pg_query_parse() function as parser.parse_sql_json()

  • Expose the new pg_query_parse_protobuf() function as parser.parse_sql_protobuf()

  • Expose the new pg_query_deparse_protobuf() function as parser.deparse_protobuf()

  • Honor the catalogname of a RangeVar if present (issue #71)

  • Cover almost all SQL statements, testing against the whole PostgreSQL regression suite (issue #68, PR #72 and PR #77), thanks to Ronan Dunklau and Hong Cheng

  • New rudimentary support for the preserve comments feature (issue #23)

Breaking changes
  • Target PostgreSQL 13

  • The pglast.parser module exposes all libpg_query entry points, even the new pg_query_deparse_protobuf() function that is basically equivalent to RawStream-based printer

  • The split() function is now based on the lower level pg_query_split_with_xxx() functions

  • The parse_sql() function returns native Python objects, not a JSON string as before: all PG nodes are now represented by subclasses of pglast.ast.Node, without exception, even Expr and Value are there. The latter impacts on pglast.node.Scalar: for example it now may contains a ast.Integer instance instead of a Python int

  • The pgpp --parse-tree output is a pprint represention of the AST, not a JSON string as before

  • The ParseError exception does not expose the location as an instance member anymore, although its still there, as the second argument (ie .args[1]); furthermore, its value now corresponds to the index in the original Unicode string, instead of the offset in the UTF-8 representation passed to the underlying C function

Version 2

2.0.dev3 (2021-02-20)

  • Handle INCLUDE clause in IndexStmt (PR #67), thanks to Ronan Dunklau

2.0.dev2 (2020-10-24)

  • Merge new fingerprint functionality from v1 (i.e. master) branch

2.0.dev1 (2020-09-26)

  • Require Python 3.6 or greater

  • Handle ALTER TYPE .. RENAME VALUE in AlterEnumStmt (PR #52), thanks to Ronan Dunklau

  • Add support for Create / Alter / Drop PROCEDURE (PR #48), thanks to Ronan Dunklau

  • Use Ronan’s fork of libpg_query, targeting PostgreSQL 12.1 (PR #36)

  • Change get_postgresql_version() to return a (major, minor) tuple (issue #38)


  • Handle PG12 materialized CTEs (issue #57)

  • Support column numbers in ALTER INDEX (PR #58), thanks to Ronan Dunklau

  • Handle SET LOGGED and SET UNLOGGED in ALTER TABLE (PR #59), thanks to Ronan Dunklau

  • Handle ALTER TYPE ... RENAME (PR #62), , thanks to Ronan Dunklau

Version 1

1.18 (2021-06-01)

  • Fix exclusion constraint printer (issue #81)

1.17 (2021-02-20)

  • Fix the generic case in the RenameStmt printer

1.16 (2021-02-20)

  • Promote to the stable state

  • Move the job of building and uploading binary wheels from TravisCI to GitHub Actions

1.15 (2021-02-19)

  • Fix IF EXISTS variant of RenameStmt printer (PR #70), thanks to Jonathan Mortensen

  • Update libpg_query to 10-1.0.5

1.14 (2020-10-24)

  • Produce Python 3.9 wheels, thanks to cibuildwheel 1.6.3

  • Expose the libpg_query’s fingerprint functionality (PR #64), thanks to Yiming Wang

1.13 (2020-09-26)

  • Handle SELECT FROM foo

1.12 (2020-06-08)

  • Double quote column names in the TYPE_FUNC_NAME_KEYWORDS set (issue #55)

  • Possibly wrap SELECT in UNION/INTERSECT between parens, when needed (issue #55)

1.11 (2020-05-08)

  • Fix A_Expr printer, when lexpr is missing (PR #54), thanks to Aiham

  • Support DISABLE ROW LEVEL SECURITY in AlterTableCmd (PR #49), thanks to Ronan Dunklau

  • Implement CreateOpClassStmt printer (PR #47), thanks to Ronan Dunklau

1.10 (2020-01-25)

  • Fix collation name printer (PR #44), thanks to Ronan Dunklau

  • Implement CreatePLangStmt printer (PR #42), thanks to Bennie Swart

  • Fix privileges printer (PR #41), thanks to Bennie Swart

  • Handle TRUNCATE event in CreateTrigStmt printer (PR #40), thanks to Bennie Swart

  • Fix function body dollar quoting (PR #39), thanks to Bennie Swart

1.9 (2019-12-20)

  • Prettier INSERT representation

1.8 (2019-12-07)

  • Prettier CASE representation

  • New option to emit a semicolon after the last statement (issue #24)

1.7 (2019-12-01)

  • Implement NotifyStmt printer

  • Implement RuleStmt printer, thanks to Gavin M. Roy for his PR #28

  • Fix RenameStmt, properly handling object name

  • Produce Python 3.8 wheels, thanks to cibuildwheel 1.0.0

  • Support ALTER TABLE RENAME CONSTRAINT (PR #35), thanks to Ronan Dunklau

1.6 (2019-09-04)

  • Fix issue with boolean expressions precedence (issue #29)

  • Implement BitString printer

  • Support LEAKPROOF option (PR #31), thanks to Ronan Dunklau

  • Support DEFERRABLE INITIALLY DEFERRED option (PR #32), thanks to Ronan Dunklau

1.5 (2019-06-04)

  • Fix issue with RETURNS SETOF functions, a more general solution than the one proposed by Ronan Dunklau (PR #22)

  • Allow more than one empty line between statements (PR #26), thanks to apnewberry

1.4 (2019-04-06)

  • Fix wrap of trigger’s WHEN expression (issue #18)

  • Support for variadic functions (PR #19), thanks to Ronan Dunklau

  • Support ORDER / LIMIT / OFFSET for set operations (PR #20), thanks to Ronan Dunklau

  • Implement ConstraintsSetStmt and improve VariableSetStmt printers

1.3 (2019-03-28)

  • Support CROSS JOIN and timezone modifiers on time and timestamp datatypes (PR #15), thanks to Ronan Dunklau

  • Many new printers and several enhancements (PR #14), thanks to Ronan Dunklau

  • Expose the package version as pglast.__version__ (issue #12)

1.2 (2019-02-13)

  • Implement new split() function (see PR #10)

  • Implement BooleanTest printer (issue #11)

1.1 (2018-07-20)

  • No visible changes, but now PyPI carries binary wheels for Python 3.7.

1.0 (2018-06-16)

0.28 (2018-06-06)

  • Update libpg_query to 10-1.0.2

  • Support the ‘?’-style parameter placeholder variant allowed by libpg_query (details)

0.27 (2018-04-15)

  • Prettier JOINs representation, aligning them with the starting relation

0.26 (2018-04-03)

  • Fix cosmetic issue with ANY() and ALL()

0.25 (2018-03-31)

  • Fix issue in the safety belt check performed by pgpp (issue #4)

0.24 (2018-03-02)

  • Implement Null printer

0.23 (2017-12-28)

  • Implement some other DDL statements printers

  • New alternative style to print comma-separated-values lists, activated by a new --comma-at-eoln option on pgpp

0.22 (2017-12-03)

  • Implement TransactionStmt and almost all DROP xxx printers

0.21 (2017-11-22)

  • Implement NamedArgExpr printer

  • New alternative printers for a set of special functions, activated by a new --special-functions option on pgpp (issue #2)

0.20 (2017-11-21)

  • Handle special de-reference (A_Indirection) cases

0.19 (2017-11-16)

  • Fix serialization of column labels containing double quotes

  • Fix corner issues surfaced implementing some more DDL statement printers

0.18 (2017-11-14)

  • Fix endless loop due to sloppy conversion of command line option

  • Install the command line tool as pgpp

0.17 (2017-11-12)

  • Rename printers.sql to printers.dml (backward incompatibility)

  • List printer functions in the documentation, referencing the definition of related node type

  • Fix inconsistent spacing in JOIN condition inside a nested expression

  • Fix representation of unbound arrays

  • Fix representation of interval data type

  • Initial support for DDL statements

  • Fix representation of string literals containing single quotes

0.16 (2017-10-31)

  • Update libpg_query to 10-1.0.0

0.15 (2017-10-12)

  • Fix indentation of boolean expressions in SELECT’s targets (issue #3)

0.14 (2017-10-09)

  • Update to latest libpg_query’s 10-latest branch, targeting PostgreSQL 10.0 final

0.13 (2017-09-17)

  • Fix representation of subselects requiring surrounding parens

0.12 (2017-08-22)

  • New option --version on the command line tool

  • Better enums documentation

  • Release the GIL while calling libpg_query functions

0.11 (2017-08-11)

  • Nicer indentation for JOINs, making OUTER JOINs stand out

  • Minor tweaks to lists rendering, with less spurious whitespaces

  • New option --no-location on the command line tool

0.10 (2017-08-11)

  • Support Python 3.4 and Python 3.5 as well as Python 3.6

0.9 (2017-08-10)

  • Fix spacing before the $ character

  • Handle type modifiers

  • New option --plpgsql on the command line tool, just for fun

0.8 (2017-08-10)

  • Add enums subpackages to the documentation with references to their related headers

  • New compact_lists_margin option to produce a more compact representation when possible (see issue #1)

0.7 (2017-08-10)

  • Fix sdist including the Sphinx documentation

0.6 (2017-08-10)

  • New option --parse-tree on the command line tool to show just the parse tree

  • Sphinx documentation, available online

0.5 (2017-08-09)

  • Handle some more cases when a name must be double-quoted

  • Complete the serialization of the WindowDef node, handling its frame options

0.4 (2017-08-09)

  • Expose the actual PostgreSQL version the underlying libpg_query libray is built on thru a new get_postgresql_version() function

  • New option safety_belt for the prettify() function, to protect the innocents

  • Handle serialization of CoalesceExpr and MinMaxExpr

0.3 (2017-08-07)

  • Handle serialization of ParamRef nodes

  • Expose a prettify() helper function

0.2 (2017-08-07)

  • Test coverage at 99%

  • First attempt at automatic wheel upload to PyPI, let’s see…

0.1 (2017-08-07)

  • First release (“Hi daddy!”, as my soul would tag it)

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