PostgreSQL
Comparing PostgreSQL Plans Before and After a Change
Compare PostgreSQL query plans before and after a change: capture both, control cache and noise, line up nodes and decide if the gain is real or warm cache.
7 min read
Library
Everything you need to level up your coding skills.
JSON
Finding One Bad Line in a Huge JSON Lines File Fast
Locate the malformed record in a large JSON Lines file with jq, Python, awk and DuckDB, why parser line numbers drift, and how to split good from bad.
7 min read
PostgreSQL
Why the Planner Estimates the Wrong Number of Rows
Why the PostgreSQL planner estimates the wrong number of rows: stale statistics, skew, correlated columns, expressions and parameters, with the fix for each.
7 min read
JSON
Validating Text as JSON With json_valid in SQLite Tables
What json_valid accepts in SQLite with each flag, why a CHECK can pass a NULL, how to find bad rows, add a check to an existing table and check JSONB blobs.
7 min read
XML
Debugging an XSLT Transform That Outputs Nothing or Too Much
Five stylesheets that output nothing or the whole file as text, with the cause of each: a namespace, a built-in rule, an absolute path, and a literal id.
7 min read
Excel
Fixing Duplicate Column Names When Reading Excel Data
Handle duplicate column headers when reading Excel in pandas, Power Query and SQL loads: automatic suffixes, safe renaming and what duplicates mean.
7 min read
JSON
Fixing Invalid JSON Text Errors in MySQL Inserts and Imports
Decode MySQL error 3140 Invalid JSON text and its relatives, including the backslash trap in SQL string literals that silently changes your JSON.
9 min read
Excel
Excel Cell Contains More Than 32767 Characters Error
Excel allows 32767 characters per cell and draws only 1024. See what happens to longer text on import, export and in scripts, and where to store it.
6 min read
Excel
Fixing Circular Reference Warnings in Imported Sheets
Why imported Excel sheets warn about circular references, how to find the loop with the trace tools, and the fix for each cause in formulas and scripts.
7 min read
Excel
Excel Formula Shows as Text Instead of Calculating
Fix an Excel formula that shows as text instead of a result: Text format, Show Formulas, a leading apostrophe, manual calculation and scripts.
7 min read
Excel
Fixing BadZipFile When Reading an XLSX With Python
Fix zipfile.BadZipFile File is not a zip file when openpyxl or pandas reads an xlsx: wrong content, empty or truncated file, encryption and upload mistakes.
7 min read
Excel
Fixing the Python xlrd Error Excel xlsx Not Supported
Fix XLRDError Excel xlsx file not supported in pandas and Python: xlrd 2 reads only old xls files, so install openpyxl and pick the right engine.
6 min read
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