6 Commits (2fcedad3cac54ec01034f3e225dd7915e59ff8ff)

Author	SHA1	Message	Date
Tom Lane	d5b132bb62	Dodge portability issue (apparent compiler bug) in new tablesample code. ... Some of the older OS X critters in the buildfarm are failing regression, with symptoms showing that a request for 100% sampling in BERNOULLI or SYSTEM methods actually gets only around 50% of the table. gdb revealed that the computation of the "cutoff" number was producing 0x7FFFFFFF rather than the expected 0x100000000. Inspecting the assembly code, it looks like gcc is trying to use lrint() instead of rint() and then fumbling the conversion from long double to uint64. This seems like a clear compiler bug, but assigning the intermediate result into a plain double variable works around it, so let's just do that. (Another idea would be to give up one bit of hash width so that we don't need to use a uint64 cutoff, but let's see if this is enough.)	11 years ago
Tom Lane	6fcb337fa5	Redesign tablesample method API, and do extensive code review. ... The original implementation of TABLESAMPLE modeled the tablesample method API on index access methods, which wasn't a good choice because, without specialized DDL commands, there's no way to build an extension that can implement a TSM. (Raw inserts into system catalogs are not an acceptable thing to do, because we can't undo them during DROP EXTENSION, nor will pg_upgrade behave sanely.) Instead adopt an API more like procedural language handlers or foreign data wrappers, wherein the only SQL-level support object needed is a single handler function identified by having a special return type. This lets us get rid of the supporting catalog altogether, so that no custom DDL support is needed for the feature. Adjust the API so that it can support non-constant tablesample arguments (the original coding assumed we could evaluate the argument expressions at ExecInitSampleScan time, which is undesirable even if it weren't outright unsafe), and discourage sampling methods from looking at invisible tuples. Make sure that the BERNOULLI and SYSTEM methods are genuinely repeatable within and across queries, as required by the SQL standard, and deal more honestly with methods that can't support that requirement. Make a full code-review pass over the tablesample additions, and fix assorted bugs, omissions, infelicities, and cosmetic issues (such as failure to put the added code stanzas in a consistent ordering). Improve EXPLAIN's output of tablesample plans, too. Back-patch to 9.5 so that we don't have to support the original API in production.	11 years ago
Tom Lane	131926a52d	Remove useless check for NULL subexpression. ... Coverity rightly gripes that it's silly to have a test here when the adjacent ExecEvalExpr() would choke on a NULL expression pointer. Petr Jelinek	11 years ago
Tom Lane	2aa0476dc3	Manual cleanup of pgindent results. ... Fix some places where pgindent did silly stuff, often because project style wasn't followed to begin with. (I've not touched the atomics headers, though.)	11 years ago
Bruce Momjian	807b9e0dff	pgindent run for 9.5	11 years ago
Simon Riggs	f6d208d6e5	TABLESAMPLE, SQL Standard and extensible ... Add a TABLESAMPLE clause to SELECT statements that allows user to specify random BERNOULLI sampling or block level SYSTEM sampling. Implementation allows for extensible sampling functions to be written, using a standard API. Basic version follows SQLStandard exactly. Usable concrete use cases for the sampling API follow in later commits. Petr Jelinek Reviewed by Michael Paquier and Simon Riggs	11 years ago