Contents

• pgPDF: pdf type for Postgres
  • Usage
    • String Functions and Operators
    • Full-Text Search (FTS)
    • Document similarity with pg_trgm
    • Metadata
  • Installation
    • Docker

pgPDF: pdf type for Postgres

This extension for PostgreSQL provides a pdf data type and assorted functions.

You can create a pdf type, by casting either a text filepath or bytea column.

SELECT '/tmp/pgintro.pdf'::pdf;

                                       pdf                                        
----------------------------------------------------------------------------------
 PostgreSQL Introduction                                                         +
 Digoal.Zhou                                                                     +
 7/20/2011Catalog                                                                +
  PostgreSQL Origin 

If you don’t have the PDF file in your filesystem, but have already stored its content in a bytea column, you can just cast it to pdf.

SELECT pg_read_binary_file('/tmp/pgintro.pdf')::bytea::pdf;

Why?: This allows you to work with PDFs in an ACID-compliant way. The usual alternative relies on external scripts or services which can easily make your data ingestion pipeline brittle and leave your raw data out-of-sync.

The actual PDF parsing is done by poppler.

Also check blog:

• Full Text Search on PDFs With Postgres
• pgpdf: pdf type for Postgres

Usage

Download some PDFs.

wget https://wiki.postgresql.org/images/e/ea/PostgreSQL_Introduction.pdf -O /tmp/pgintro.pdf
wget https://pdfobject.com/pdf/sample.pdf -O /tmp/sample.pdf

Create a table with a pdf column:

CREATE TABLE pdfs(name text primary key, doc pdf);

INSERT INTO pdfs VALUES ('pgintro', '/tmp/pgintro.pdf');
INSERT INTO pdfs VALUES ('pgintro', '/tmp/sample.pdf');

Parsing and validation should happen automatically. The files will be read from the disk only once!

[!NOTE] The filepath should be accessible by the postgres process / user! That’s different than the user running psql. If you don’t understand what this means, as your DBA!

String Functions and Operators

Standard Postgres String Functions and Operators should work as usual:

SELECT 'Below is the PDF we received ' || '/tmp/pgintro.pdf'::pdf;

SELECT upper('/tmp/pgintro.pdf'::pdf::text);

SELECT name
FROM pdfs
WHERE doc::text LIKE '%Postgres%';

Full-Text Search (FTS)

You can also perform full-text search (FTS), since you can work on a pdf file like normal text.

SELECT '/tmp/pgintro.pdf'::pdf::text @@ to_tsquery('postgres');

 ?column? 
----------
 t
(1 row)

SELECT '/tmp/pgintro.pdf'::pdf::text @@ to_tsquery('oracle');

 ?column? 
----------
 f
(1 row)

Document similarity with pg_trgm

You can use pg_trgm to get the similarity between two documents:

CREATE EXTENSION pg_trgm;

SELECT similarity('/tmp/pgintro.pdf'::pdf::text, '/tmp/sample.pdf'::pdf::text);

Metadata

The following functions are available:

• pdf_title(pdf) → text

• pdf_author(pdf) → text

• pdf_num_pages(pdf) → integer

  Total number of pages in the document

• pdf_page(pdf, integer) → text

  Get the i-th page as text

• pdf_creator(pdf) → text

• pdf_keywords(pdf) → text

• pdf_metadata(pdf) → text

• pdf_version(pdf) → text

• pdf_subject(pdf) → text

• pdf_creation(pdf) → timestamp

• pdf_modification(pdf) → timestamp

SELECT pdf_title('/tmp/pgintro.pdf');

        pdf_title        
-------------------------
 PostgreSQL Introduction
(1 row)

SELECT pdf_author('/tmp/pgintro.pdf');

 pdf_author 
------------
 周正中
(1 row)

Getting a subset of pages

SELECT pdf_num_pages('/tmp/pgintro.pdf');

 pdf_num_pages 
---------------
            24
(1 row)

SELECT pdf_page('/tmp/pgintro.pdf', 1);

           pdf_page           
------------------------------
 Catalog                     +
  PostgreSQL Origin         +
  Layout                    +
  Features                  +
  Enterprise Class Attribute+
  Case
(1 row)

SELECT pdf_subject('/tmp/pgintro.pdf');

 pdf_subject 
-------------
 
(1 row)

SELECT pdf_creation('/tmp/pgintro.pdf');

       pdf_creation       
--------------------------
 Wed Jul 20 11:13:37 2011
(1 row)

SELECT pdf_modification('/tmp/pgintro.pdf');

     pdf_modification     
--------------------------
 Wed Jul 20 11:13:37 2011
(1 row)

SELECT pdf_creator('/tmp/pgintro.pdf');

            pdf_creator             
------------------------------------
 Microsoft® Office PowerPoint® 2007
(1 row)

SELECT pdf_metadata('/tmp/pgintro.pdf');

 pdf_metadata 
--------------
 
(1 row)

SELECT pdf_version('/tmp/pgintro.pdf');

 pdf_version 
-------------
 PDF-1.5
(1 row)

Installation

Install poppler dependencies

Linux

sudo apt install -y libpoppler-glib-dev pkg-config

Homebrew/MacOS

brew install poppler pkgconf

cd /tmp
git clone https://github.com/Florents-Tselai/pgpdf.git
cd pgpdf
make
make install # may need sudo

After the installation, in a session:

CREATE EXTENSION pgpdf;

Docker

Get the Docker image with:

docker pull florents/pgpdf:pg17

This adds pgpdf to the Postgres image (replace 17 with your Postgres server version, and run it the same way).

Run the image in a container.

docker run --name pgpdf -p 5432:5432 -e POSTGRES_PASSWORD=pass florents/pgpdf:pg17

Through another terminal, connect to the running server (container).

PGPASSWORD=pass psql -h localhost -p 5432 -U postgres

[!WARNING] Reading arbitrary binary data (PDF) into your database can pose security risks. Only use this for files you trust.