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Commit3cc0800

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Add a transform function for numeric typmod coercisions.
This enables ALTER TABLE to skip table and index rebuilds when a columnis changed to an unconstrained numeric, or when the scale is unchangedand the precision does not decrease.Noah Misch, with a few stylistic changes and a fix for an OIDcollision by me.
1 parentaf7914c commit3cc0800

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4 files changed

+53
-2
lines changed

4 files changed

+53
-2
lines changed

‎src/backend/utils/adt/numeric.c

Lines changed: 48 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,8 @@
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#include"catalog/pg_type.h"
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#include"libpq/pqformat.h"
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#include"miscadmin.h"
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#include"nodes/nodeFuncs.h"
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#include"parser/parse_clause.h"
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#include"utils/array.h"
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#include"utils/builtins.h"
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#include"utils/int8.h"
@@ -712,6 +714,52 @@ numeric_send(PG_FUNCTION_ARGS)
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}
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/*
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* numeric_transform() -
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*
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* Flatten calls to our length coercion function that solely represent
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* increases in allowable precision. Scale changes mutate every datum, so
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* they are unoptimizable. Some values, e.g. 1E-1001, can only fit into an
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* unconstrained numeric, so a change from an unconstrained numeric to any
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* constrained numeric is also unoptimizable.
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*/
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Datum
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numeric_transform(PG_FUNCTION_ARGS)
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{
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FuncExpr*expr= (FuncExpr*)PG_GETARG_POINTER(0);
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Node*typmod;
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Node*ret=NULL;
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if (!IsA(expr,FuncExpr))
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PG_RETURN_POINTER(ret);
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Assert(list_length(expr->args)==2);
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typmod=lsecond(expr->args);
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if (IsA(typmod,Const))
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{
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Node*source=linitial(expr->args);
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int32old_typmod=exprTypmod(source);
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int32new_typmod=DatumGetInt32(((Const*)typmod)->constvalue);
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int32old_scale= (old_typmod-VARHDRSZ)&0xffff;
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int32new_scale= (new_typmod-VARHDRSZ)&0xffff;
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int32old_precision= (old_typmod-VARHDRSZ) >>16&0xffff;
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int32new_precision= (new_typmod-VARHDRSZ) >>16&0xffff;
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/*
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* If new_typmod < VARHDRSZ, the destination is unconstrained; that's
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* always OK. If old_typmod >= VARHDRSZ, the source is constained.
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* and we're OK if the scale is unchanged and the precison is not
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* decreasing. See further nodes in function header comment.
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*/
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if (new_typmod<VARHDRSZ|| (old_typmod >=VARHDRSZ&&
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new_scale==old_scale&&new_precision >=old_precision))
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ret=relabel_to_typmod(source,new_typmod);
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}
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PG_RETURN_POINTER(ret);
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}
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/*
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* numeric() -
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*

‎src/include/catalog/catversion.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,6 @@
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*/
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/*yyyymmddN */
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#defineCATALOG_VERSION_NO201201311
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#defineCATALOG_VERSION_NO201202071
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#endif

‎src/include/catalog/pg_proc.h

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2142,8 +2142,10 @@ DATA(insert OID = 2917 ( numerictypmodinPGNSP PGUID 12 1 0 0 0 f f f t f i 1
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DESCR("I/O typmod");
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DATA(insertOID=2918 (numerictypmodoutPGNSPPGUID121000ffftfi102275"23"_null__null__null__null_numerictypmodout_null__null__null_ ));
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DESCR("I/O typmod");
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DATA(insertOID=1703 (numericPGNSPPGUID121000ffftfi201700"1700 23"_null__null__null__null_numeric_null__null__null_ ));
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DATA(insertOID=1703 (numericPGNSPPGUID121003157ffftfi201700"1700 23"_null__null__null__null_numeric_null__null__null_ ));
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DESCR("adjust numeric to typmod precision/scale");
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DATA(insertOID=3157 (numeric_transformPGNSPPGUID121000ffftfi102281"2281"_null__null__null__null_numeric_transform_null__null__null_ ));
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DESCR("transform a numeric length coercion");
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DATA(insertOID=1704 (numeric_absPGNSPPGUID121000ffftfi101700"1700"_null__null__null__null_numeric_abs_null__null__null_ ));
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DATA(insertOID=1705 (absPGNSPPGUID121000ffftfi101700"1700"_null__null__null__null_numeric_abs_null__null__null_ ));
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DESCR("absolute value");

‎src/include/utils/builtins.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -913,6 +913,7 @@ extern Datum numeric_recv(PG_FUNCTION_ARGS);
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externDatumnumeric_send(PG_FUNCTION_ARGS);
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externDatumnumerictypmodin(PG_FUNCTION_ARGS);
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externDatumnumerictypmodout(PG_FUNCTION_ARGS);
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externDatumnumeric_transform(PG_FUNCTION_ARGS);
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externDatumnumeric (PG_FUNCTION_ARGS);
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externDatumnumeric_abs(PG_FUNCTION_ARGS);
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externDatumnumeric_uminus(PG_FUNCTION_ARGS);

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