simultaneously-created tables not generating

i have three clients connected to one mserver. they are simultaneously running these three commands, which share table `z` but not the x or y tables-- CREATE TABLE y1 AS SELECT x1.* FROM x1 LEFT JOIN SELECT col FROM Z ON x1.id = z.id WITH DATA ; CREATE TABLE y2 AS SELECT x2.* FROM x2 LEFT JOIN SELECT col FROM Z ON x2.id = z.id WITH DATA ; CREATE TABLE y3 AS SELECT x3.* FROM x3 LEFT JOIN SELECT col FROM Z ON x3.id = z.id WITH DATA ; when all three commands complete, tables y2 and y3 do not exist if i run the commands sequentially, everything works. am i making a mistake in how sql transactions should behave, or is this potentially a bug that i should figure out how to reproduce for bugzilla? thanks!