Adam BookLaugh

Warszawa, Polska

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BookLaugh / set_sequence_values.py

Last active October 27, 2016 11:26

PostgreSQL procedure for updating all sequences used as default values for table columns. Once called, it will update values of sequences to max value present in column plus 5 (why 5? So you can find out which sequences were altered). Function returns list of names of updated sequences.

	CREATE OR REPLACE FUNCTION set_seq_vals(schema_name TEXT)
	RETURNS TEXT[]
	AS $$
	schemaname = schema_name if schema_name else 'public'
	plpy.execute("SET SEARCH_PATH=%s,public" % schemaname)
	tables = plpy.execute("SELECT tablename FROM pg_tables WHERE schemaname = '%s'" % schemaname);
	altered_seqs = []
	for t in tables:
	cols = plpy.execute("SELECT column_name, column_default, data_type, is_nullable FROM information_schema.columns WHERE table_name = '%s' AND data_type in ('integer', 'bigint') AND column_default IS NOT NULL" % t["tablename"])
	for c in cols:

jboner / latency.txt

Last active December 23, 2025 06:41

Latency Numbers Every Programmer Should Know

	Latency Comparison Numbers (~2012)
	----------------------------------
	L1 cache reference 0.5 ns
	Branch mispredict 5 ns
	L2 cache reference 7 ns 14x L1 cache
	Mutex lock/unlock 25 ns
	Main memory reference 100 ns 20x L2 cache, 200x L1 cache
	Compress 1K bytes with Zippy 3,000 ns 3 us
	Send 1K bytes over 1 Gbps network 10,000 ns 10 us
	Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD