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TABLESAMPLE, SQL Standard and extensible

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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
This commit is contained in:
Simon Riggs
2015-05-15 14:37:10 -04:00
parent 11a83bbedd
commit f6d208d6e5
66 changed files with 2756 additions and 40 deletions
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60
src/backend/nodes/copyfuncs.c
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@@ -641,6 +641,22 @@ _copyCustomScan(const CustomScan *from)
return newnode;
}
/*
* _copySampleScan
*/
static SampleScan *
_copySampleScan(const SampleScan *from)
{
SampleScan *newnode = makeNode(SampleScan);
/*
* copy node superclass fields
*/
CopyScanFields((const Scan *) from, (Scan *) newnode);
return newnode;
}
/*
* CopyJoinFields
*
@@ -2063,6 +2079,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
COPY_SCALAR_FIELD(rtekind);
COPY_SCALAR_FIELD(relid);
COPY_SCALAR_FIELD(relkind);
COPY_NODE_FIELD(tablesample);
COPY_NODE_FIELD(subquery);
COPY_SCALAR_FIELD(security_barrier);
COPY_SCALAR_FIELD(jointype);
@@ -2224,6 +2241,40 @@ _copyCommonTableExpr(const CommonTableExpr *from)
return newnode;
}
static RangeTableSample *
_copyRangeTableSample(const RangeTableSample *from)
{
RangeTableSample *newnode = makeNode(RangeTableSample);
COPY_NODE_FIELD(relation);
COPY_STRING_FIELD(method);
COPY_NODE_FIELD(repeatable);
COPY_NODE_FIELD(args);
return newnode;
}
static TableSampleClause *
_copyTableSampleClause(const TableSampleClause *from)
{
TableSampleClause *newnode = makeNode(TableSampleClause);
COPY_SCALAR_FIELD(tsmid);
COPY_SCALAR_FIELD(tsmseqscan);
COPY_SCALAR_FIELD(tsmpagemode);
COPY_SCALAR_FIELD(tsminit);
COPY_SCALAR_FIELD(tsmnextblock);
COPY_SCALAR_FIELD(tsmnexttuple);
COPY_SCALAR_FIELD(tsmexaminetuple);
COPY_SCALAR_FIELD(tsmend);
COPY_SCALAR_FIELD(tsmreset);
COPY_SCALAR_FIELD(tsmcost);
COPY_NODE_FIELD(repeatable);
COPY_NODE_FIELD(args);
return newnode;
}
static A_Expr *
_copyAExpr(const A_Expr *from)
{
@@ -4179,6 +4230,9 @@ copyObject(const void *from)
case T_CustomScan:
retval = _copyCustomScan(from);
break;
case T_SampleScan:
retval = _copySampleScan(from);
break;
case T_Join:
retval = _copyJoin(from);
break;
@@ -4842,6 +4896,12 @@ copyObject(const void *from)
case T_CommonTableExpr:
retval = _copyCommonTableExpr(from);
break;
case T_RangeTableSample:
retval = _copyRangeTableSample(from);
break;
case T_TableSampleClause:
retval = _copyTableSampleClause(from);
break;
case T_FuncWithArgs:
retval = _copyFuncWithArgs(from);
break;