LIMIT 10 doesn't make it cheaper: BigQuery bills the bytes it reads, not the rows it returns
A SELECT * with LIMIT 10 returns ten rows and can still bill the whole table. How BigQuery stores and reads data, and how to make every query read less.
Blog
One mistake per post. Each one comes from a short video and goes further: a step-by-step animation, the cause, the fix and how to check it.
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Every day, every time: querying the GA4 export's events_* with no _TABLE_SUFFIX filter
Without a _TABLE_SUFFIX filter, events_* reads every day you've exported, plus intraday tables with streaming on. Higher bills and totals that don't match.
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One purchase, six rows: CROSS JOIN UNNEST(event_params) before counting in the GA4 export
Unnesting event_params with a CROSS JOIN turns each event into one row per parameter, so COUNT and SUM multiply. How to read parameters without duplicating events.
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Two users, one session: counting GA4 sessions in BigQuery with ga_session_id alone
ga_session_id only identifies a session within one user, so COUNT(DISTINCT ga_session_id) merges sessions of different users. How Google counts them instead.
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The purchase moves to yesterday: taking the day from event_timestamp in the GA4 export
event_timestamp is in UTC, while event_date follows the property's time zone. Take the day from the timestamp and events near midnight land on the wrong day.
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Every sale counted twice: broken deduplication between the Pixel and the Conversions API
When the Pixel and the Conversions API send the same purchase with different event_ids, Meta can't deduplicate it and counts it twice. How to share one ID.
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Hashing the wrong fields: which user_data fields get SHA-256 in the Conversions API
Email and phone get SHA-256; IP, user agent, fbc and fbp don't. Mix them up and Meta matches fewer events. Which fields to hash and how to normalize them.
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Sales that lose their click: a stale or altered fbc in the Conversions API
fbc changes with every ad click and is case-sensitive. Stored once or normalized, the conversion travels with the wrong click. How to send it correctly.
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One late event sinks the whole batch: the 7-day event_time limit in the Conversions API
If a single event in the request has an event_time older than 7 days, Meta returns an error and processes none of them. Why it happens and how to avoid it.
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Wrong key events: when GA4 conversions aren't outcomes
Marking page_view or scroll as key events, or sending purchase with no value or currency, turns conversion rates and ROAS into meaningless numbers.
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Your team inflates the reports: internal and test traffic in GA4
Staging, QA, your own team and the agency: traffic that isn't customers, mixed with the real one. Why an IP filter isn't enough and how to exclude it properly.
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Customer emails stored in GA4: personal data in your URLs
A form submitted by GET leaves the email in the URL, and GA4 stores it in page_location. That breaks its terms. How to remove it at the source and clean up.
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Your campaigns end up in “Unassigned”: UTMs outside the channel rules
A utm_medium the channel rules don't recognise lands in Unassigned, and black_friday and Black_Friday are two different campaigns. How to clean up your UTMs.
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In DebugView, but not in your reports: unregistered custom dimensions
GA4 collects every parameter you send, but only shows it in reports once it is registered as a custom dimension. And registering is not retroactive.
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Revenue that doesn't match the backend: mistakes in the GA4 purchase event
value as text, no currency and an empty transaction_id: three mistakes in the purchase event that make GA4 lose or duplicate revenue.
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One user counted as two: cross-domain measurement in GA4
When the journey jumps between domains, GA4 may create a new client_id on the second one. How to configure the domains and check that _gl gets through.
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PayPal takes the credit for your sales: payment gateways as referrals in GA4
If paypal.com shows up as the source of your purchases, the return from the gateway is being logged as new traffic. The unwanted referrals list fixes it.
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Page views counted twice: the duplicate page_view in GA4
When two sources send the same page_view, GA4 doubles views and events while traffic stays flat. How to find the second source and remove it.
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GA4 cookies before consent: the Consent Mode default arrives too late
If GA4 writes cookies before the user answers the banner, the usual culprit is load order: the Consent Mode default state is declared too late.
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