Tag
cardinality
- May 27, 2026 Head-Based Sampling: Where the Decision Belongs and What It Costs How probabilistic and rate-limiting samplers make the keep-or-drop call at trace start, why the decision must be consistent across the trace, and how the sampled flag makes it authoritative downstream. observability
- Feb 9, 2026 Mini-Dimensions and Junk Dimensions: Narrowing a Wide Fact Table How to keep fast-changing attributes out of a versioned dimension, and how to collapse a handful of low-cardinality flags into one key instead of a dozen foreign keys. data engineering
- Dec 30, 2025 Fleet-Wide Alerting and the Per-Instance Rule Why the aggregation level of an alerting rule decides both what it can detect and how many notifications it produces, and how to choose between per-instance, per-shard, and fleet-wide evaluation. observability
- Nov 18, 2025 Selectivity Estimation from Histograms and Most-Common-Value Lists How a single-column statistic turns a predicate into a row count, why equidepth buckets are chosen over equiwidth, and where the estimate fails for correlated columns. databases
- Sep 8, 2025 How Null Rates and Distinct Counts Detect a Broken Join Column profiles are cheap aggregates that catch errors no type check can: a null-rate jump or a collapsed distinct count localises a fault to one column. data engineering
- Jul 5, 2025 Cardinality Control in Metric Pipelines Why label combinations explode faster than series limits expect, how aggregation drops dimensions, and what a pipeline can do when the limit is already exceeded. observability
- Jun 24, 2025 Dictionary Encoding and the Cardinality Cliff How replacing repeated values with ordinals shrinks a column, why the win collapses as distinct values grow, and what happens to a column chunk when the dictionary outgrows its budget. data engineering
- Jan 31, 2025 Structured Fields Versus Formatted Message Strings What is lost when a log record is a printf template, how field-value encoding preserves types, and why templates still matter for cardinality. observability
- Dec 4, 2024 How a Query Cost Model Reduces I/O and CPU to One Number Why planner costs are weighted units rather than milliseconds, how sequential and random page reads enter the sum, and which effects the arithmetic deliberately ignores. databases
- Sep 15, 2024 Learning Optimizers: Learned Cardinality Models and Plan Regression What a learned selectivity model replaces in the catalog, why a plan that is cheaper on average can be a regression for one query, and how plan management contains the damage. databases
- Jul 12, 2024 Join Cardinality and Where the Containment Assumption Fails How equality joins are estimated from distinct-value counts, why the uniform-frequency assumption collapses on skewed keys, and how the error compounds across a chain of joins. databases
- Apr 24, 2024 Adaptive Plans: Choosing the Join Algorithm After Execution Starts How a statistics collector at a plan node defers the choice between nested loop and hash join, what the switch costs mid-flight, and why re-planning after a blocking operator is a different mechanism. databases
- Feb 29, 2024 Cardinality Explosion and Where It Comes From How label combinations multiply into series count, why an unbounded label value destroys an index, and which containment measures actually bound the growth. observability
- Jul 11, 2023 Adaptive Sampling: Feedback Control over Span Volume How a sampler adjusts its rate from observed traffic instead of a fixed configuration, why per-operation rates are needed, and the statistical damage caused by a rate that keeps changing. observability
- Sep 5, 2022 Repeat Suppression and Template Fingerprints How collapsing identical messages into a count preserves signal, why a fingerprint must be computed over the template rather than the text, and where collapsing loses information. observability