XML
Why Excel Complains About an XML Source Having No Schema
When Excel says the XML source has no schema, it infers one. What the guess means, why it breaks on optional and repeating data, and how to supply a schema.
5 min read
Tag
explainer
59 posts
YAML
Storing YAML Text in a Database Column and Its Pitfalls
What goes wrong when YAML is kept as text in a column: LIKE misses, equal documents compare unequal and garbage is accepted. The jsonb alternative fixes each.
6 min read
CSV
Selecting CSV Columns With cut and Why Quotes Break It
cut -d, -f picks CSV columns until a quoted comma shifts every field after it. See the failure, a guard that detects it, and CSV-aware replacements.
8 min read
Excel
Why Excel Is Slow With Formulas Over Many Rows Explained
Why Excel slows down with many formulas: the calculation chain, volatile functions, whole column references and scanning lookups, and how to find the cost.
8 min read
CSV
Why pandas Turns ZIP Codes Into Numbers and How to Stop It
pandas read_csv infers a column of digits as integers, so 02134 becomes 2134. See the cause, the 190,451 broken codes in 2M rows, and the fixes that work.
7 min read
PostgreSQLGuide
Reading EXPLAIN ANALYZE Output in PostgreSQL Step by Step
Read EXPLAIN ANALYZE output in PostgreSQL: plan tree, cost, rows and loops, scan and join nodes, BUFFERS, sorts, estimates and a way to find the slow step.
18 min read
XML
What an XML External Entity Attack Is and Where It Works
An XXE attack makes a parser read a file or fetch a URL the sender names. Run on five parsers, three leaked a local file by default or with one flag.
7 min read
XMLGuide
XML Security Problems to Close Before Production Launch
The XML attacks that matter for web services and loaders, how six parsers behave, one parse function with limits, and the tests that keep it closed.
18 min read
CSV
Why SQLite Stores Your CSV Numbers as Text and How to Fix It
SQLite .import stores every CSV value as text, so ORDER BY puts 10.25 before 2.75 and amount > 9 matches every row. See the cause and three ways to fix it.
8 min read
Excel
Why SQL Beats Formulas Once the Data Gets Large and Slow
Why spreadsheet formulas slow down as data grows and where SQL pulls ahead: lookup cost, recalculation, memory, repeatability and auditability.
7 min read
Excel
Why an Exported Excel Date Shows as a Number and the Fix
An exported date shows as 45292 because Excel stores dates as numbers and the cell has no date format. See the cause, the code fix and a file repair.
7 min read
XML
Should You Store XML in a Database Column or Shred It
Store XML whole, shred it into tables, or both? What each engine keeps and loses, what validation you get, and what it costs on 200,000 documents.
7 min read